I like the idea, and I think it has some usefulness. Sure, it won't save your base if tyrants attack one a focused point, but it provides "maintenance" repairs, saving builders the time it takes to repair a turrets that dretches just run up against and damage, or damage done in an alien attack to buildings not directly attacked, but hurt (by explosions, etc.).
However, Patriotpie makes a good points... with the current (unfinished) 1.2 changes aliens are a little underbalanced (if that's a term), and this wouldn't help them.