To import you would need the same number of animations that the IE engine uses. Which I think is 14. They would have to be placed in the same order, in a file of the same format as all the other BG animations.
You wouldn't be able to make the .cre use any other weapon then the one linked to his animation. Well, you could, but it would look silly, a knight swinging his sword and someone gets hit by a bolt. Since to add a ranged attack for the knight, you would have to edit all of the frames to give him different weapon.
I'd suggest that you extract a couple of animations from BG2, making sure you get a walking and attacking animation. Just so you can see how many frames you are going to need and how they are set up. Then extract one from D2 and see if the animations match up, if they don't, I wouldn't advise it.
At 14 animations to complete one action (like attacking), and the action can be performed while facing 9 different directions.... And there are many actions.... You can see why most people don't bother with new graphics.