Well, here are a few weapons where I'd think an additional mode could be added.
Iberian Mace - should be able to use 2h for more damage, but maybe slower.
Staves - should be able to switch to twohanded mode without thrust (or the normal polearm thrust), but slowed down accordingly.
Spears - should be able to switch to onehanded usage (like it is with shields) at will. Yeah, I know it's not really good, but sometimes your shield breaks and all you want is a long thrust.
Goedendag - should be able to use it like a spear (gripped in the middle) together with a shield and no speed penalty.
Barmace - normal mode without crushthrough, secondary slower mode with crushthrough.
