Hi Max,
Since you first posted this idea, I have been looking at the difference between the LWB and the SWB models.
The 109" wb has a little more panel length between the door and the rear wheelarch (where the rear door would be), and more overhang at the back of the wheelarch to the backpanel.
As Joakim says though, a second row of seats will be right where the motors go, so unless you plan on using a mobility scooter motor / transaxle, and mounting it below the floor pan, then you are heading for problems.
I have no doubt that it can be done, but some 'Lateral' thinking will have to be applied.
Personally, I hope you work it out, I would love to see it at one of the meetings!
Good Luck,
Regards,
mark.