I like the weapon special attacks. Ofc they're not all equally good, so work could definitely be put into adjusting them to be more useful.
I'd also be happy with a bigger change: making weapon abilities unlimited usage but coming with a penalty. E.g:
- Rush could have a -2 to hit on all attacks and provoke AoO from those targets.
- Cleave could be a -5 to hit on all attacks.
- Pin Down could be a -2 to hit and the target makes a Strength ST. If they fail, their movement is reduced by half (not just 3m).