Seems to me that if you're performing a docking procedure on a vessel that is large enough for a bow thruster the engine would always be running.

I'd make serious consideration of putting a battery up front and use it for the thruster and windless as well. The weight shouldn't be an issue as the extra weight isn't that much considering the size and displacement. If the vessel was so small the weight would make a difference it wouldn't need a bow thruster. The weight of 60' of cable 'although displaced throughout the front half' would weigh about the same as a forward battery instillation. Put it under the rear of the V-birth.

I always wanted a thruster but the Admiral feels it will make me a poorer sailor and she's always impressed with me being able to jockey the boat in tight quarters. (she doesn't care that I'm sweating the entire time.)