If you are looking to record drums in your new space, your problem will be your ceiling height. Sound naturally wants to go up more than sideways.(where you have plenty of room). The best drum rooms in the world(for eg Avatar/Power Station) have tall ceilings and its not gigantic(L x W). Your best bet is to use your control room space for drums(taller ceilings) and use the live room space for the control room(you can get away with a lower ceiling).
And to answer your other question, yeah I am sure you can get someone to design it for your price. The big costs will be in labor/construction and materials, not to mention your HVAC system.
You can always hire someone in town to build it with the acoustician designs. You would just have to serve as your own foreman and watch there work carefully.