Cool looking bent so far, in either RWD or FWD. I was going to suggest the same thing about the idler pulley sticking out too far in FWD mode and causing knee clearance issues, but if you've got no problem with it, the dual pulley certainly simplifies things. Sometimes with a pulley up around there, it can be a good idea to put some kind of simple guard on it to prevent greasing up the inside of your leg, hitting your leg or pulling out leg hairs if they get too close to the pulley-chain combination. We had minor issues with that on our Nitro clone, and our pulley was only about 3/4" thick and close enough to the frame to just allow the chain past the head tube.
http://fleettrikes.com/nitro%20clone%20pulley.jpg
As for gear ranges, we had the same concerns with 20" drive wheels. My Speed came with a 52T top gear and I ran out of gears on a very slight decline on the first ride on it. I switched out the original triple and replaced it with a 60/40 double and I'm pretty happy with the gear range with a 9 speed 34/11 cassette. I've had it up to just a little over 85 kph and haven't spun out yet with 110 gear inches in high gear, but I have 130mm cranks on it too. It gives a low gear of 25 gear inches which has been fine so far for some fairly steep climbs and some long climbs around here, but I don't have grade numbers to quantify it unfortunately. Vuelta makes some nice, and inexpensive over sized chainrings but they only seem to come in 110 BCD. I made a simple adapter to fit it to a 130BCD spider though. With a long cage RD, it manages to soak up the extra chain when I go down onto the 40T ring, and the only gear I lose is the 11T, so I still manage to use 17 of 18 gears. I was also concerned with how well it would shift between the 60 and 40T rings, but it's as smooth as the original triple.
http://fleettrikes.com/cs618%2060%2040%20chainrings.jpg
Another option that allows you to use more conventional road triples is to use a Shimano Capreo hub. It comes as a 9 speed, with a 26T - 9T range. I've seen a couple of these in use and the guys drilled their cassettes and replaced a couple of the larger gears so they could use a 30 and 32T for some better hill gearing. You have to buy the cassette with the hub, and I've seen them come in 32 and 36 spoke drillings. Sheldon Brown has a lot of information about them and also sells them.
http://sheldonbrown.com/capreo/index.html
Lastly, in experimenting with different 20" (406) tires that are smooth, narrow and high pressure, I've found that some of them can reduce the tire diameter to 18", which further reduces the top speed a little. I like the Stelvios because they're the best ones that I have access to for their cost, and they are pretty close to 18" final diameter. The high pressure Kenda Kwests would be my #2 choice, again for the price/availability criteria.
I'm looking forward to seeing the progression.