Moving to Switzerland for health reasons. What can go wrong with my plan?

Hi all. I have a complication after a knee surgery. The only place that can treat it well in Europe seems to be in Lugano, Switzerland. Luckily, my job is open to letting me move and work as a contractor from Switzerland. Currently I am based in Germany and a Polish citizen, so luckily an EU passport.

My plan is: 1. Find a place and get registered there (maybe city pop for the first few months, than see. The price seems reasonable, I can book it online and it should give me the right papers to register). 2. Get a work permit. My salary would probably stay the same as in Germany (88k CHF, gross). I assume I would work via an agency to make sure everything is legal. So there will be their fees 3. Get insurance 4. Get surgery and physical therapy I need (might be more than one surgery) while working remotely.

Some caveats: 1. Risk that the work permit takes a while. What does it mean for me? Can I continue working for Germany (it should be ok for up to 90 days, afaik?)? Can I apply before even living there, with some sort of an offer letter? 2. Insurance refuses to treat my knee because it's definitely pre-existing and I can't really hide that I can barely walk. However, I don't think I can be denied basic medical care. Can someone confirm? 3. Finding the best insurance: one that is not a pain to deal with, pays in time, etc. 4. As a contractor, I probably don't get sick leave and vacations. So I need to financially prepare for being off for a month after surgery, and anything unexpected that might happen.

Other than that, I think my plan could work. What are other risks? And what do you think about those above?

Please refrain from any hate. I just need my knee to work again and I can't get the treatment I need in Germany. I'd much rather not go through this.