I dont understand why no one has mad a shaft drive yet.
You could used flanged drive shaft through the chainstay.... so when it pivots away from the bb its still enganged on the shaft.
You could fit at least 8 gears inside a rear hub, and use a pull bar in the center to engauge diferent gears,... there fore alowing a trigger shifter.
The bb would have to be designed like a differential,... with a primary drive either coming from the side, underneath or center rear of the bb.
Seeing as the torge figure wouldnt be that much either you could even used flexible shafts like that on flexie extention bars for you rachet. [wrench]

I dunno just an idea... seams cheaper with less material, thus less weight to. Oh and trigger shifter instead of gay grip shit