Just love when people have gone thru their own analysis, come up with a solution that works for them and ask questions only to have others hijack their request and offer their own opinions based on their personal wants/needs or analysis.
I've looked into doing this too. There are people who have successfully flat towed the Smart Car and they say a manual transmission isn't required. See
this link. One other solution is to trailer the Smart Car and there are a couple of manufacturers that have trailers designed for this purpose. I found four, but only three appear to still be in business. Try this
one manufacturer,
this one, and
this one.