Ok, I gave 4th ed a good try. I ran the group up to 27th level. I hated almost every min of it. I have no idea why I stayed with it for so long. But it had one truly great idea that OSR can steal: At will attacks.
The idea is that you give everyone several dif basic attacks that they can switch between, fighter are the ones most in need of this. Some examples from my OSR/3.5/4th mash up:
Every time you miss w/ a melee attack you get +1 to hit (max +3)
every time you hit you get +1 to damage( max +3)
+2 to hit but you do ONLY basic weapon damage
Every time you hit you get 2 temp HP
1/2 damage but opponent is -2 to hit
you can only do one of them at a time and it should scale w/ L, Fighters should get about 4 and everyone ese should get 2(they should be appropriate to char cass) You do only basic attacks on charge and AoO