Mommus,
The electrical load of your idea might not be that big a deal...if you factor in diversity.
For example, on a 250 seat 787, how many people will be operating their seat motors simultaneously? Probably guess no more than around 20 or so. So you only need to allow capacity for 20 rather than 250...throw in some wriggle room, and you might say 30.
I'd be more concerned at the combined weight of all those motors and associated wiring...