There is also LR with delta-wye switching for the motor. That would give you two speeds for the motor, with a ratio change of 1.73:1. There are lots of hubs with disc mounts on the LH side, but ideally you'd want to add the sprocket in a way that lets you keep the disc. I don't have any bikes here with disc brakes, so it is a bit hard to visualize how this could work, or if it is even possible.
I also want to do a single-speed cruiser-type bike RRsetup, with a FW for the pedals, like I have on my folding bike setup, and direct drive for a delta-wye configured motor. Most of these bikes have coaster brakes and I'm having a hard time getting my head around what would happen to the brake operation, with the extra freewheel. Would it still work?
Nope. I personally don't see that as a loss.There are also lots of Nexus-3 - equipped beach cruisers around here that also have coaster brakes.
Regarding Matt's comment about chain clearances, I now find this to be less of a problem than it was when the motor was also spinning the pedal chain. I had a heck of a time, because the spring-loaded tensioner I was using would unload when the motor was driving the chain, causing it to slap into the #35 motor chain. Several times this caused the bike chain to come off, the last time locking up the back wheel. With my new setup, with the freewheel in back, the chain does move when the motor is on, so problem solved.
Also, the chains just ended up farther apart with the new setup.
Anything that eliminates the need for spinning another chain is a good thing from a safety and reliability perspective. The freewheeling front cranks seems like a very band-aid type solution IMO.
Regarding use of #219 chain/sprockets, I have another idea. If we use one of the 3/4" motor sprockets, from GoKartGalaxy, there are oneway bearings available from McMaster that have 3/4" OD and can handle up to 6.5 ft-lbs, or 8.9 Nm (is that enough?). They have inside diameters of 1/2", though, so I'd have to get Bob to do 1/2" shafts for the 32 series. It is not clear to me, however, how the shaft would attach to the oneway. Press-fit, I guess?
One-way's normally just freely slide over a shaft like a set of needle bearings. Each needle is has an oval shaped cross section and a tiny spring steel band with slots to act as a spring for each needle sits sandwiched between the cage for the needles. When a tiny amount of friction tries to go backwards, they decrease the size as the oval needles rotate backwards, as the size decreases, it eventually seizes to the shaft, gripping, until forward motion releases everything. Because the oval needles can't spin, they do not work as a bearing at all, so you need dual bearings to support the 1-way if you wish it to not quickly wear out.That's a pain. I think instead I'd have my guy do a custom adapter that he can press into the oneway that then has a hub with a couple of setscrews and an ID of 3/8" so it can fit the existing motors.
The needle 1-ways all work off friction from shrinking the ID. Even if it has 10 times the torque rating of the motor, I still find them to be a short lived band-aid type fix. I see them as designing in an Achilles heal in a system that could otherwise be very reliable. In my limited personal experience with them in everything from auto-trannys to RC cars, they've always been another wear part to fail in a system. Just my $0.02
-- Gary
I should have thought of that, would have been a lot easier 
