You want at least a 45’ wide door, AT6 has 42.5’ wingspan. I would also go with a door tall enough to fit an Aerocommander tail. Talk to builder sometimes the sweet spot for hanger wall eave height might be 14’ or 16’ or 18k. Ie cost difference maybe pennies to go taller. Down here in North Texas you really want the main door opening to face south, blocks hot sun, and cold winds. South is also our prevailing wind, so a overhead door on the north side of the hangar for RV(retirement vehicle) access allows cross flow ventilation. Make sure a pedestrian door is nearby to both doors, and that they are all visible from house or neighbors. A toilet and water is a necessity. Can also have bathroom build as a concrete block FEMA tornado shelter, if those are ever a problem in your area. Insulation is easier done in construction than retro fit. I don’t like rolling doors, you have to either push-pull a plane over the track, or you have a cavity type track you have to vacuum out.. I’d prefer a bifold, hydroswing, or a tip up door. A hangar I recently visited, had car lifts, a full kitchen. A built in pressure washer, hot water hose bibs. You can go all out with plumbed air hose connections etc etc. Look at the Drago guy’s hangar, he has a car mounted on one wall, with a board/meeting room. If you are up north headed floors are handy too.