honestly the thing i REALLY don't want is the game to stray too far from what was advertised (i.e. a sudden genre change for stupid reasons) it's a 3-d open-ish world platformer. keep it that way. there CAN be some gimmicks to spice up the game here and there (for instance, a small minigame here and there) but at its core, yooka-laylee is a 3-d platformer with a heavy emphasis on exploration.
one other thing that comes to mind of things i don't want is in difficulty: don't make it too hard or too easy. there HAS to be a balance between challenge and fun. and don't throw in blatantly broken missions either (clinkers cavern, the ordinance storage, and canary mary come to mind when it comes to broken missions) don't make the game so hard it scares casuals away but don't make it too easy as to bore us.