GLSL? Low level shaders? Heh, I remember using that a long time back in some OGRE demos...
Personally, I don't think Glest needs it. What I think Glest needs for models is:
-Lighting (would be uber awesome to be able to do this)
-Improved transparency (I don't think the bug where the transparency shows right to the ground, through the model has been fixed yet...)
-Multi-part models, which some can rotate to attack and some parts wont (aka: rotating cannons. MANY games use this. An example is how a tank will have two parts, the main body which stays fixed when rotating to attack (but not to move) and the cannon part which rotates as normal to attack).
-More methods of particle effects, particularily for splashes, such as a fire-like effect, etc; Personally, I'd like to see sprite compatibility (I know some guy once modified the engine to show a 2D image above the units that rotated to face the camera, kinda sprite like... Still, sprites would be awesome).
Of course, as Wciow said, the biggest problem is lack of a graphics coder... Maybe we have been neglecting time spent on programing boards to recruit programmers?
You know what, I'm going to go to a board right now, make an account, and try and get a few people interested. Wish me luck!