Mixing it up

I understand the usual recommended "prescription" plan for weightlifting results to gain muscle as alternating pull day/push day/leg day (or some variation) doing 3 sets of 8-10 reps and going to fatigue. Getting a little dull and want to mix it up. I was thinking about substituting days with light weights high reps/ days of heavy weight where I can only do 3 reps/ days of "exercises I generally never do" and days of calesthetics. Any thoughts on how this might positively or negatively affect my ulrimate goal to build muscle, strength and definition? I know there are lots of opinions out there so most interested in ones that have some science behind them. Thanks!