https://www.youtube.com/watch?v=krD4hdGvGHMGoing to bring up the old thread again, I have been thinking recently and I have an Idea for a 4 door version.
It would be difficult to make a 6x6 4 door FEMTT, but I think it might be possible to make a 6x8 version by adding a non powered Steering Axle to the front of the Donor vehicle to make something that looks similar to the HEMTT A3 Hybrid, The engine would be behind the 2nd axle (1st axle on stock Donor vehicle)
If you're tall (like me) you would have plenty of leg room in the 2nd row, you might even be able to make it into a sleeper.
It would be possible to make the new 1st axle powered, but i'm not sure if it would be worth the headache,
but again, theoretically it would be possible to do.