I am a modder, I developed a dynamic wave generation system last year.

[Lirania]

Only thing I would suggest is to have it so the harder bots cannot be randomly spawned until halfway through the game or so to prevent something like siege masters and jotnes on wave 5 or Veteran Pikemen on wave 7. Other than that this will def make games a lot less stale.

As i can say,the point of this is,to be very challenging.(atleast i think so!) So i would say throw Jotnes at us. Give that mode a lvl 52 cap.
We are not talking about 50 Jotnes on wave 4...maybe 6 or so.
I hope its gonna be heavily team based.