I like your idea! After playing vanilla or even a mod several times, the player tends to learn and remember the 3D layout of each base facility they use. Then in the next game played, the player uses that knowledge when planning the layout of his bases from a defense standpoint. But in playing vanilla or a mod for the first time, the player has little idea what each facility looks like in 3D until one of his bases is under attack. It would be nice to be able to see the base 3D layout when deciding where to construct a new facility. The 3D view would include existing base with the new facility in the player chosen spot prior to commencing construction.
I realize the player can use sources outside of the game (ie strategy guide, wikipedia, etc) to get base layout planning information, but this risks the player being spoiled by coming across things he hasn't seen in the game yet. Once research unlocks a new facility the player can now use, the player should know the 3D layout of the facility prior to building one especially for these mods that use additional levels with various access points blocked.
After all, one wouldn't build a house without knowing what was on each floor or where the doors and stairways are.
