Crimson Flower is shorter than the other routes, but its chapters of the same number are more difficult (in terms of enemy levels) than the other routes. Therefore, the appropriate length for CF considering its difficulty curve is 20 chapters, such that enemies reach lv50 in the final chapter similar to the other routes. Adding 2 in-fill chapters is a reasonable solution since there is no reason why the empire falls after 4 battles (Myrddin, Gronders, Merceus, Enbarr city+palace) whereas the kingdom falls in 3 and alliance in 2.

Hence, I present with the following ideas.

Ch13

Same Myrddin, with Lorenz replacing Leonie (Claude, Holst and Judith put pressures on House Gloucester to defend the alliance, even if he is unwilling) and he can be spared to join the army; and 2 generic snipers replacing Ignatz.

Ch14

In-fill chapter 'Will of the Alliance'

Story: After capturing the Great Bridge of Myrddin, the Black Eagle Strike Force decided to march through the now headless Daphnel territory to lay siege on Derdriu, expecting few resistance from the fallen house. However, they were surprised to encounter a sizable army consisted of commoners from all walks of life, rallied together under a mercenary-turned general, intercepting their advance towards the Alliance capital.

Chapter mission battle: the Daphnel Breakthrough.

The same map as Death Toll and Land of the golden deer, with 1 drawbridge permanently lowered and the other dismantled.

Objective: Defeat the enemy commander.

The enemies to the left are named 'mercenary'; those to the right are named 'alliance knight'; those near the river are named 'rogue'; and those at the back are named 'alliance militia'.

Player turn 1

Leonie/Alliance general: As citizens of the free Leicester Alliance, we have responsibilities to be the sword and shield of our Alliance,

Leonie: and to uphold the spirit of the infamous Blade Breaker against those who have betrayed him.

Leonie/Alliance general: We cannot allow our homeland to fall to the Empire!

Alliance soldiers: Fight!!!

Hubert: The enemies are large in numbers, but they do not seem to be well-trained or maintained. We can capture the fortress and secure our way to Derdriu if we exploit their individual weakness.

Leonie only starts moving when attacked, or when both Ignatz and Raphael (or their replacements) are defeated. (8 move 4 range bow knights are known to suicide onto the player from the opposite side of the map otherwise) Every other enemy unit will follow her and charge the player when this happens.

Reinforcement spawns when a player unit enters the yellow box, and every 2 turns thereafter.

Enemy reinforcement: Alliance Militia: Our families and businesses are behind this stronghold. We cannot let it fall!

Enemy Ignatz dialogue: same as base game Myrddin.

Enemy Raphael dialogue:

VS anyone: If you're gonna cause harm to my sister and grandpa, I'm gonna beat you down!

VS Byleth: I've got no idea why you joined Edelgard, but I can't welcome you here.

VS Ignatz: Ignatz: I can't bring myself to fight you, Raphael. How can I face Maya after this?

Raphael: Then outta my way and leave the Empire. I don't wanna fight you too.

Ignatz: I'm sorry...

Death: Maya... Take care... Without me...

Enemy Leonie dialgue: same with base game Myrddin, but with AM Gronder death quote.

Mission completed: Edelgard: People of Leicester, your commander has fallen. Any more resistance is futile. Surrender, and we will not persecute.

Back in the Monastery: (Byleth looks troubled)

Edelgard: My professor, are you still troubled by the past battle?

Byleth: Is it really justified to claim civilian lives for our goal?

Edelgard: As long as they are holding a weapon, they are combatants.

Edelgard: Besides, they may be against us and die fighting our army, but their lives otherwise would also have been consumed by the church and their deceptive teachings if we had not raised our army against the Church of Seiros.

Edelgard: It is unfortunately a necessary evil for our road ahead. We share this pain together, my professor.

Ch15-17

Same Derdriu&Garreg Mach&Arianrhod

Ch18

In-fill Chapter 'Descendants of a Hero'

Story: Upon witnessing the fate of Count Rowe and Arianrhod, the western Kingdom lords are gathered by Baron Dominic, whose ancestry traces back to the Elite Dominic, to set up defence in Brennius territory between Arianrhod and Blaiddyd territory. The Black Eagle Strike Force, seeing no alternatives, decided to launch a full-on assault on Brennius territory in order to approach Fhirdiad.

Chapter mission battle: Subjugating the Western Kingdom.

The same map as The Forgotten, True Chivalry, and Weathervanes of Fodlan

Objective: Defeat all enemy commanders.

Player turn 1

Baron Dominic: As the descendant of Elite Dominic, I hereby declare this stronghold to be the last stand of western Kingdom. We shall protect it even at the cost of our own lives.

Hubert: Pathetic mindset. Crests and bloodlines will soon be a thing in the past under Empire rules.

Gilbert and Annette arrive when a player unit reaches the 9th row or below.

Enemy reinforcement: Baron Dominic: Reinforcement from the capital has arrived! Thank you, my brother and little niece. (last 3 words are omitted if Annette has been recruited)

Viscount Brennius (if he is still alive): Begin the counterattack at once! (Any surviving troops around Viscount Brennius and Belinus start too move towards the player, along with the reinforcements. Both gates on Brennius's side open.)

Enemy dialogues:

Viscount Brennius:

VS anyone: I shall drive the Empire into the dirt!

Death: I may fall... But the Kingdom will live... Under His Majesty...

Yvette: No! We promised to be rivals forever.

Viscount Belinus:

VS anyone: Our faith rests on this strategy. I cannot lose here!

Death: My strength flees... The rest is in your hands...

Brennius: My rival... I pledge to avenge you!

Count Duval:

VS anyone: For my land and people, I cannot give in.

Death: There's no escape... Goddess above, I beg you to watch over the people of Faerghus...

Baron Dominic:

VS anyone: House Dominic may be only the lord to a Barony, but our might in fighting shall live up to the name of the Elite.

VS Byleth: So the new Nemesis of the Empire is here. When the leader goes on a stray path, it comes to the subordinate to stop him/her. (Depends on Byleth's gender)

VS Annette: Baron Dominic: So my brother is true about my niece joining the Empire.

Baron Dominic: If you have your reasons to betray the kingdom, I have my reasons to strike you down.

Annette: I am sorry, my uncle... But I believe in my path.

If he is the last commander remaining: Baron Dominic: Though our fates may be sealed, we will fight to the very last... (starts moving with his troops if not already so)

Edelgard: How stubborn. Victory will be ours.

Death: And so I reach my end... Pray forgive me my weakness, my brother, and Your Majesty.

Gilbert: I will let the Empire pay for what they have done to Faerghus and to House Dominic!

Gilbert:

VS anyone: No one will ravage these lands while I still draw breath. I will lay the lot of you low!

VS Byleth: (Uses base game Fhirdiad dialogue)

VS Annette: (Uses base game Fhirdiad dialogue)

Defeat: Gilbert: That is all the fight I have left in me... I have to support the royal house.

Baron Dominic: Thank you, my brother, you can leave the rest too me.

Annette:

VS anyone: It is sad seeing familiar faces in battle, but for Faerghus and for House Dominic, I can't let you pass.

VS Byleth: Professor, it's really you! I am grad you are still alive, but we can't go back to the monastery days.

VS Mercedes: Annette: Mercie... You chose to return to the Empire at the end. I guess it can't be helped.

Mercedes: Annie... I am so sorry. I really enjoyed my time in the Kingdom, but now isn't the time to reminisce....

Annette: I understand...

Defeat: Annette: I can't fall here. My friends in the capital still need me.

Baron Dominic: It's alright, Annette. I will handle the rest.

Mission completed:

Hubert: So that was the last of them. How pitiful it is to die for an outdated belief.

Edelgard: The enemies have fought bravely. The Empire should benefit greatly if only some of them could have been turned to our side.

Edelgard: (To Hubert and Byleth) Those people in the dark... They will pay for Arianrhod.

Back in monastery:

Edelgard: The fixation on crests and bloodlines is ingrained in the Kingdom houses. House Dominic is not the only example. We all have witnessed what transpired at Conand Tower five years ago. It is time to change the falsified history and belief that leads to the bloodshed in Brennius, and uncountably many other places.

Hubert: Well said, Your Majesty. We must prevail if we are to change the world. This war is only the first step.

Byleth: So it is the world itself that we have been fighting against.

Edelgard: Yes, my professor. With you leading us, we can achieve victory.

Ch19-20

Same Tailtean&Fhirdiad. With a few dialogue changes to account for repeated encounters.

Gilbert VS Annette

Gilbert: So you still have the heart to invade Fhirdiad after you killed your own uncle in Brennius? You are not my daughter!

Annette: Whatever you may believe, father. Be warned that I will push you aside, even if I must use force to do it.

Gilbert: Goddess...this is surely a chastisement from you.

Gilbert VS Byleth:

Gilbert: The goddess shall not condone your repeated atrocities in Brennius and Tailtean Plains. For His Majesty and for my family, your life ends here.

Annette VS Byleth

Annette: Why, Professor? Why must we fight like this again? Surely there was another path you could have taken that wouldn't have led to this...