There are a lot of variable you haven't addressed. For instance, is it clear span, or do you have support members? Where are the doors? How do you prefer to manage the work flow.....the car moves to the stall for each operation, or does the tech move from car to car while the car stays in a fixed stall (except for paint probably)? Do you have/want a clean area that is separated by fixed walls, or is it feasible to use curtains? And much much more.

Here's one of the options I used when I had my shop. My body shop supplies vendors had computer design programs for doing shop layouts. These took into account the things DW talked about and more. If they believed you'd be buying some of the equipment/fixtures from them they would do the design service for free.