I like the idea, to be quite honest. Of course though, if the building is destroyed, it should not have that 15-second grace period.
If you think about it logically, if an alien attacks your power-source, it's going to attack the power source in a way that will destroy it, no matter how they have to do it. If you deconstruct it, then you can take it apart in a manner which would allow the buildings to function for a short period of time.
This will also reduce the number of people who spawn builder in the beginning of the game just to see the RC go down and not be able to do anything until the RC is back up except blaster.
Another thing it would do is reduce the number of cheap games that occur when one alien walks by a turret and notices the RC is down, thusly calling in a fleet of dretches to antagonize all the poor humans waiting for their RC to come back up. It'll provide a bit of a shield.
Since the RC takes, what? 20/30 seconds to build, 15 seconds would still allow for time for the buildings to not function correcly so aliens will have a glimmer of opportunity to get into the base, but it will make games more competitive, which is what everyone should look for when playing trem anyways. The more competitive a game is, usually the more fun it is, unless you just want to killwhore, but killwhoring can be done without the RC down anyways.
My $.02.
-Bull
