+1 that the idea is very good but the execution is...questionable at best. Weapon abilities should give much-needed flexibility (and weapon identity) to martial characters without being strictly more powerful options or stepping on the toes of other classes' features. The current special attacks satisfy neither of those criteria.
Larian needs to be vary wary about weapon abilities that mess with the action economy (bonus action cost and/or stunning the enemy) and need to include an appropriate drawback for each ability. E.g., doesn't do damage, attack at disadvantage, etc.
