After talking more with the player, this Mandocaster is quite similar to what I think I heard you talking about doing. I thought he'd want to play one or the other with nary a snippet between, but I didn't think that through...
He wants to do lead bits from one to another, and be able to shut one down when he wants to as well, so I do need some semblance of "blend" in that regard.
After thinking and drawing a bit, I believe I'm gonna go with a standard Tele control panel, the three single coils, (I have a Duncan set for the Tele and a custom for the mando), with a 5 way switch a la Strat. I'll do the switching as 1-Tele lead, 2-Tele lead and Mando, 3-Mando, 4-Tele lead and bridge, 5 tele bridge. The volume knob goes to push-pull which will kill the mando signal, and tone knob push-pull kills Tele.
At least I think so right now...
Urb