I'd like to suggest the following change that will hopefully be possible using WSE that would make shield walls a bit more useful imo.
Whenever you kick somebody that is blocking with a shield, it takes your strength and their shield skill into account to decide if the kick is successful.
I would say that Strength has to be greater than the shielders base skill + 2x the shield wall boost. This means that shield walls with the current skill boosts will become extremely difficult to break up with kicks and they will require Maulers and Cav to break them (or superior tactics). Meanwhile a lone shielder is still easy to kick as even if they have 13 shield skill, you only need 14 strength to successfully kick them.
Failed kicks that still connect should still stun the shielder but in a way that does not remove their blocking shield. This means they can't retaliate, but they aren't left vulnerable either.
EDIT: Just realised the maths didn't quite work so I've changed it slightly