@grogerson (I believe he is the author of the BG Tweak Pack)
In the BG Tweak Pack there is a tweak which lets you change your one handed bastard swords into two handed bastard swords (and back again). This changes their damage from 2D4 to 2D5 and their speed factor from 8 to 9. I'm thinking out loud here, but that seems to invalidate two handed swords (which do 1D10 damage with a speed factor of 10). The two handed bastard swords in the tweak are now faster than two handed swords and also have the advantage of doing 2D5 damage over 1D10.
Perhaps the tweak should modify the two handed bastard swords differently? Classic two handed swords should still do superior damage, so maybe leaving bastard swords wielded with two hands doing 2D4 damage and dropping their speed factor from 8 to 7 or 6 would be a better option. It would after all, seem to make sense that you'd be able to wield the same sword more quickly using both of your hands over just using one. Two hands/arms = more muscle with which to manipulate the sword that weighs the same amount regardless of whether or not you're using one hand or two. Thoughts?