Pops - Thanks for sharing those.
After a quick Google search I found a few more…
Although I'm not convinced you could make a panel kit that would look like any of these when bolted to one of these.
Having said that, the first two (red & yellow) cars you posted do look like they are working with the Smart car's curved door.
And we have all followed the miracles that Chris & Dan create @ Tribute.
Personally, I think they would need to convert the roadster into a Coupe (like the Z3 to SWB 250 conversion).
Then aim for something like this.
But extend both the bonnet and boot away from the wheels until it was a
bit closer to the real proportions.
Cheers, Paul.