If the avatars aren't going to be animated, I think it would look better if only the party leader's tile is displayed when moving around, then break out the whole team when combat begins. Are there still going to be attacking/casting animations? Replacing animated guys, even if they only have 2 or 3 animations, with still images is a big change. The animations in Helherron for example are bare-bones simple but IMO they add a lot to the experience. I never get tired of seeing the wind-up before the attack.
One tip I wanted to share with Helherron fans: there were three different places where I would get combat crashes and I finally figured a way around it. The crashes all had grid bugs in play and if I avoided casting any spells which leave graphics on screen, like Create Great Fire and Web, the game wouldn't crash.