Separate finishing room... good! 8'x8'? Go a little bigger, especially with such a large shop. You need room to be able to maneuver larger pieces and get completely around them with out bumping into walls. More space will help you do that.

You don't say where you are located, but you do indicate that heat will be required. By all means consider in-floor radiant right from the start. Very comfortable and efficient. But also consider breaking up the space a little more and put in a zoned system so you can heat even more economically. That's a big space! Storage can be heated less or even unheated much of the time. You might also consider a separate assembly room in that respect.

For any large exterior doors, use roll-ups rather than garage doors that take up overhead space. And don't forget natural light. Even if you put windows high up on the wall, don't leave them out.