I was an avid base builder, I would say to some degree I still am, only I don't have CoH, I just fiddle with minecraft for hours. It spoils me because it's like a huge set of infinite legos, but like CoH it was mildly unsatisfying because there wasn't enough control, or there wasn't a specific thingy.
This leads me to the point, first is that I HATE flat instances, in a 3D environment, stacking areas of an instance should be EASY, perhaps with limitations, but in the RP I'm doing here, our base is in a clock tower, and I'd be truly disappointed if we couldn't make this.
CoH was annoying in a lot of other ways, for instance, setting up areas to be designated hallways and rooms, while I think there should be some assurance people can get through, this could be done with a secondary checker tool to ensure there's some path in the 3D space to a given area. It was truly irksome to have an amazing base set up, the theme in one instance was a warehouse, so sometimes a blank hall wasn't a bad thing, but for other designs like caves and sewers, a square wall didn't work!
There was also the matter of being incapable of building working objects, this I can understand, it's hard to animate polygons, but other games have shown that players can and do grasp the idea of coding an object to move in a space (Furcadia being one niche example of instance coding, granted 2dimensionally)
These really are things other players mentioned or had contention with.
1. Give us control over the shape of the instance(3Dimensionally stacking open spaces, making cones, of curves, or domes), and what we want where, don't make give the rooms arbitrary categories to limit what you put in them, sometimes we've only got to rooms to work with.
2. Let us build some objects, perhaps we pick a category of object and we compile it from pieces provided, designate a function to a polygon section, voila, you made your own teleporter.
3. Provide us with common sensible objects that everyone can use, it would be nice to even have doors, so I don't know, we could lock a room in the instance!
I don't think these are weird or hard to do, just block it out, this section is shaped like a cave, this like a sewer pipe, and so on. I hope others agree with me, sorry if this should go someplace else...