I would love to have a removable tail because it would make transportation to and from the field much easier for me. I think the hangar 9 design would be the one to go with because you could install flying wires and not have to take them off everytime you took the tail off. I think 72" length would be about right with a wing span in the 67-68" area. This may need to be scaled down a tiny bit more as others have suggested to maybe 66" wingspan to save a little more weight.

You should have an optional hardware kit made of high quality parts that includes everything except radio gear and the engine so that when someone starts building this thing he does't have to go to the LHS 3 or 4 times for the small little things.
I would want ailerons on mine to be sticking out of the wing. It may not look as nice but I've never seen a setup for in wing servos that was a strong as just using 2 servo rails.

Again rudder servo position should be optional either it's something you ask your costumers before you build the plane or you make the aircraft so that the rudder servo could be installed in either position during final assembly.

This thread is getting really interesting.

James