Stud shooters but 1x1x3(?) cylinder bricks used instead of studs... bigger, easier-to-recover 'bullets'
Maybe a little more focus on secondary characters? Or more fan-created creations accepted into HF lore? I know I just want to see more of the creative builder aspect implemented. Like weapons that can be swapped and mounted on different pieces of cladding but interchangeable between characters or.. something.
There is a comic series on Deviantart created by a cool user, Kalhiki, sort of a retelling/continuation of the story, darker by far and in my opinion way more fun. It's more the speed I'd want a reboot to be at. Go check out "Dawn of Evil", it's good.
Also, want to see maybe a new team. Keep Furno, Breez, etc. appearing every so often, but put the focus on others and explore/expand the universe.
There's a lot I'd wanna see, heh.