Yes, it has to be engineered of course particularly with the seat belt mounts , now just to throw something in the mix , here in Melbourne there is a Traveller which according to the owner is a English import 2nd owner which was ordered from the factory with the seats facing backwards and mounted just behind the front seats and the bottom of the seat folds up and can be clipped secure so you still have load space , ingenious
To me two points stand out would be that if you did the same apart from the obvious would be replacing the battery with an Optima or similar and having it properly secured( lead acid battery near 4 people ? ) and having extra engineered mounting points for baby and child seats
Go for it
.