So, just a quick suggestion that came to me:
Why not give Fighters the possibility to take 'physical training' feats?
For example, at lvl 8 and 16, they get the chance to up one physical stat (STR, DEX, CON) by 1, in addition to the current stat increase you can do.
It's not a huge bonus, but I think it could give fighters a chance to expand on their builds? Just a thought.