A good idea for glest would be to allow for a new system of unit movement. Namely, military units would move independent of tiles. Right now, at any given moment, a unit is in one tile, never in between. This makes the units slaves to the tiles. This also makes it hard for units to travel in a straight line, or in a group without spreading, and passing between two large, impassable objects is not easily done, and any coherence of the group is lost. Many other games have this, where some units, designated as buildings, follow a strict tiles set, and others, designated as military are free to roam. This doesn't prove it is a good thing, but I think glest could use it. Glest is a game that uses small numbers (selection sizes are pretty small), but it is hard to handle even such small numbers. Other ideas for making commanding an army easier were good, but this seems like it could really help.
One way to do this would be to subdivide each tile 10 times, to make smaller tiles. I really don't know any way this could be implemented, and it might make the game run slow, but this feature could make things much more realistic.