Yes thats also one of my ideas, a D&D3.x retro mod.
For example you get ASIs independently of feats and you get them per character level, so you can raise your stats at level 4, 8, 12, always.
Also get a lot more feats. Like Combat Reflexes, an old favorite of mine. You could get as many attacks of opportunity per round as your dexterity modifier.
Another idea is a rebalance mod. Probably two actually, one for the races and one for the classes. The one for races is obviously very necessary.
Another idea is the opposite of the retro mod, a D&D5.5 improvements mod.
