Great article, Damien.
Hilleberg did make a tent with interchangeable vestibules (standard or GT version) in the past, the Stalon.
Apparently, it never sold much, so Hilleberg discontinued it. Maybe it never took off because of the weight (it was comparatively heavy).
So, Hilleberg has a solution for just what you asked for. The question is if they got their fingers burnt with the Stalon, and also if the Hilleberg solution is light weight enough.
For lighter tents, Hilleberg is starting out with a couple new 3 season tents, Anjan and Rogen. Lighter versions of their Nallo (2 and 3) and Allak.
Maybe we'll see a lighter version of the larger Nallo tents in the future too.