Wow. Thanks for the ideas. Sounds like this can be made to work. Whether it turns out to be practical is another issue. Might involve more pushing than I want. According to
Sheldon, 3.7 mph @50 rpm. Wobble, wobble, wobble. 19 mph @80. Fast enough for loaded touring.
Currently running a 9 spd cassette. 10 spd to get ultra low granny needed with 36 t chainring. Shifting precision is not a big consideration. Push/pull 'til it feels right or the limits are reached.
Like the chain-guard suggestion as I usually ride in the winter in either jeans or running pants. Sandwiching is not an option according to Cyclocross World, bolt set length being the killer. They do offer a neat dérailleur-like chain keeper.