Just a thought, but this seems like it could be a fun addition:
Heavy / Large Weapons ( Dependent on whether the weapon models CAN be made bigger in one's hand or not?)
Basically, heavy/large weapons have the following negative penalities:
5 or 10 pounds heavier then normal weapons
Attack Penalty : -2
However, because they're large/heavy weapons, their base damage is increased by one size:
1d4 becomes 1d6
1d6 becomes 1d8
1d8 & 2d4 becomes 2d6
1d10 becomes 2d8
1d12 or 2d6 becomes 3d6
Which probably will only be craftable (like double scimitars!), at first, but maybe some loot items in the future, if this might be deemed interesting?
Mind you, the Weapon Proficiency feat (Huge) should have some stringent requirement : 21+ STR, maybe?
Oh, though Fighters lvl 12+ should probably be able to get it irregardless of any requirements.
Anyway, just a thought!