I was going to agree with you if you hadn't come up with the nice idea of a bonus to bluff and the "spring to life" power. Instead, the form of an object will "come to life" in the way they make their attack (for instance, a constricting rope).Maybe signature abilities aren't actually the way to go, and it's more important to find a power that fits their form rather than their "race"? Their signature is defined by what befits their shape, not their nature.
Hmm, I would like to make a leader type monster. Any suggestions for which type of furniture/object seems like a leader type? Bookcase mayhaps?
I was considering a statue, but that may be intruding too much into Golem-land..