The part that makes it very difficult is the fact that new drive-axles (is that the right word for it?) must be made or found. Each car has its own length of suspension travel. Maybe they are right when its harder than strapping a motor to an existing gearbox. However, getting the motors to tick over should be rather straight forward. Unless their hall/ motor-position sensors are protected by a propritairy protocol. This would not stop a diy-er from directly interfacing to the hall-sensors though.
I just want that HVH250. 300+ nm torque, and a dynamic range of 0 to 13k rpm's in 1st gear with a manual transmission would redefine the word 'interesting'.
//Steven
PS: Ill try to contact AMP next week.