I doubt the engine would support it, but giving something like an AP cost reduction and damage boost for each successive strike on the same target with swords, with the same bonus for attacking different enemies in succession with polearms, would motivate some appropriate and thematic differences in play according to weapon choice. I also think melee characters would really benefit from having some actual ability to control enemy movement and attention. Maybe at certain weapon skill levels they could get a certain number of attacks of opportunity, or a higher AP cost for enemies moving through their reach, or an expanded zone of control, possibly the ability to actually pull enemies in as a battle discipline. In combination these would make combat a lot more dynamic and would leave you making more actual choices about whether you want to have your fighter standing in place to block enemy movement vs. chasing the target they would have a bonus against. You'd essentially want to have your polearm character aiming to lock a large group of enemies in place, hitting them one after the other, while sword characters are motivated to chase one big target around.