Exactly Dan,
The stainless wouldn't be as strong, especially at that length. Weight would worry me too on things like rear trailing arm bolts and front suspension arms (you know how much they twist on a standard car). What about the floor? You couldnt use a tub with glass fibre sills at that length either.
My guess is he'd want to carry the standard limo 8 passengers too. On "proper limo conversions" (at manufacturers) they consider weight load on tyres, so usually fit "commercial vehicle" tyres and steel, or stronger alloy wheels.
As an ornament it will be fine, but to drive it about or take passengers would be irresponsible.