I have wheels for my lemon, kumquat and orange bushes which are all in pots, so they can go outside for the summer - but I still have to lift them over the doorstep into the house and it's a fair old effort.

My feeling is that a holly big enough to make a decent indoor tree would have whopping heavy roots. Plus of course they are a bit spiky to shove your face into while moving the pot the way I do with the citruses!