I'm really hoping to find some nice wheels for the car. I want something taller, yet thinner. The wheel gap is crazy big and I can't see why a car this size needs 6" wide wheels at all 4 corners. I'm thinking about a staggered set-up with maybe 5.5" in the fronts and 5" in the rear, something in the 17" diameter with lower profile tires. IDEALLY lighter in weight.
I get the idea of using narrow and low-profile tires on relatively large wheels for low rolling resistance, but you're talking about abnormally narrow tires for a modern vehicle. Something that fits a Smart ForTwo might be a possibility, but then you need a wheel of that size to fit the Ford hubs, which would not match any production Ford or any aftermarket product. Also, the lower profile tire on a larger wheel will not be lighter, for the same wheel material.
Smart ForTwo sizes include:
185/50R16 (even a 5.5" wheel is not really wide enough for this)
205/45R16 (requires more than 5.5" wheel width)
Tires for the later Smart are wider than you want. Given that the Smart ForTwo is the smallest thing on North American roads, this suggests that it will be difficult to find the desired tires.
Looking at tires for the Smart, and other sizes in the same models of tires, I noticed that there are some 155/60R15. If you can find a wheel to fit, that sounds like about your target.
The Smart would also seem like a logical source of wheels suitable for these oddball tire sizes. Unfortunately, an early Smart uses three-bolt wheels, and the latest (Renault-built) generation uses a 4x100mm bolt pattern... but Ford's four-bolt small car wheels (such as the Fiesta, at least of that era) are 4x4.25" (4x108mm).
Although the vehicle may be front-heavy, a tire size bias with larger front tires is probably not a good idea.
What is the stock tire size on the Th!nk? One online source says 165/65R14 (load index 79), which was a reasonable common and functional size for this size of vehicle (but is now rare). Overall diameter would be about 570 mm or 22.5"... about an inch smaller in overall diameter than those later Smart ForTwo sizes, and matching the 155/60R15.