Watching the recent End-of-Kickstarter livestream, I got really excited when ideas for building physics were discussed. The chance to build complicated structures is made even more awesome by the chance to knock out a pillar and see the correct part of the wall fall down.
When @Tom said that building taller structures would be purely aesthetic, I thought a chance was missed for a fun mechanic. I think it would be cool if elevation increased vision. They’ve said that fog of war will be included in the game. Having a unit at higher elevation could allow that unit to see further in the fog, but he is easier to hit (to balance things out). So if I put my sentry on my top of my two story tower, he gets +1 to vision and enemies attacking him get +1 to hit. This would give some gameplay incentive for building taller structures.
This could also work for natural elevation, though that might make things more complicated to program. Units will have a radius of vision, but the radius could grow going down in elevation and shrink going up in elevation. As an example: if a unit were standing in foothills between mountains and plains, his “circle” of vision would not be a circle but would extend further into the plains and not as far into the mountains.
For melee units, who wouldn’t benefit from the extra sight once in combat, units could receive +1 damage (or +1 to critical) if attacking from a higher elevation to balance enemies getting +1 to hit against that unit.