Body shops don't work like this. Their purpose is to put butts in seats, regardless of whether or not that butt is attached to anything else that is functional. Functioning in this manner would actually be counter-productive for them, because it would reduce the number of butts that they have to put into seats, and would reduce the number of seats into which they could put butts.

If you know of a development agency, odds are that it is probably a body shop.

The places that do work like this are more like Unicorns. And Unicorns are damned hard to find and hire -- or get hired by them.