Ok, I already reached the Level 12 cap on everything, but now that the Level Cap was raised for the Steam Version of the Game, I seriously wonder what these Level Ups actually do aside from unlocking Research, because I already researched everything. Correct me if I’m wrong, but I think no high level Research Projects were added aside from the multi-platform thing.
I wonder 2 -.-
Levelling the staff does not affect research in any way, apart from the research stat for each staff member controlling how often they produce a dark blue Research Point bubble. The Design and Technology stats for each character also affect the bubbles for each area, and the Speed stat controls how often the characters stop to scratch their heads.
Raising the level caps for staff simply means you can train your staff up further to increase these stats past the old limits.
The various development categories are tied indeed tied to research, but you usually unlock the next item in each chain at around level 3 of the previous item. however you can continue to improve the levels of the individual items, and sometimes a level 6 2D Graphics V2 might just outscore a Level 3 2D Graphics V3 in the final game rating. You’ll want to experiment to find the sweet spots for your games.
Finally, if you’ve unlocked all there is to research, perhaps it’s time to start a new company and unlock it all again 
I don’t mean training the staff, I mean getting them to Level 12.
So leveling Gameplay etc. to level 12 does pretty much nothing after you unlocked all research?