Create a DFB-like instance for every zone and give incentives to run it (even for 50s).
New MM powersets (Elementals, Plants, Celestials, Goblins)
Remove Incarnates for all general content.
Remove attuned enhancements. No, you shouldn't be able to have your set bonuses of everything while exemping on a level 26 radio mission.
Re-work Independence Port and make it level 25-35. Either split the zone into two zones or reduce the size. It's too big and we all know it.
Add some incentives to go to hazard zones like Perez Park, Terra Volta, Boomtown, etc.
Make mez effects on teammates make their name/hp bar glow a certain color.
Re-work Empathy to not suck
Re-work Broadsword to not suck
Re-work Dual Blades combo system.
Re-work Controllers to allow them to hold bosses in a single application somehow. I can't get myself to even play one after playing a dom.
Re-work Brutes' Fury to be more meaningful. Fury is not that good with the current Brute damage modifier being so low.
Create content/incentives for 5-man teams. 8-man teams are too easy, with 5 each person's contributions matters much more which makes it more fun.