If I owned a small custom boat company trying to build/maintain a reputation for quality, I doubt I would sell them like that. Not that I am saying you wouldn't do a good job rigging it, but if a bunch of substandard home rigged models got on the used market it could damage the reputation of the manufacturer and the hurt the resale value for the other customers. As a manufacturer though, I would sell them completely rigged letting you supply your own power instead of using mercruiser though.
Just my 2 cents. Good luck with the project, though.