That is weapon styles' modification. Since BG engine doesn't allow the modding/modification of weapon styles one-handed fighting style is hardly useful (its unique feature, i.e., +5% critical hits/AC bonus, can be obtainable by off-hand weapons in a few mods such as IRv3).
And I have a small suggestion for additional animation.
First, as far as I know there is only one animation for Axes that show single-edged. So double-edged axe animation might be cool. In addtion, greater/giant axe animation for two-handed would be welcome, too.
Second, there were some throwing spears in several mod, but the animation seemed to be very strange. So I'd like to suggest a new animation for throwing spears.
Third, even though Throwing Hammer mod already gave the addtional throwing hammer's animation I think it might need to be added in 1PP if possible.
Lastly, the improved animation of Ioun Stone, like 1PPv4's improved spell animations, is also my wish list!