Thanks for the input. I'll see if R&M stores can order the chain tensioner + hub+ front suspension kit.

I still prefer a low-rise rear rack. I'll see if I can find one like the one used by Jon Worth that doesn't increase the folded size, and ideally let me roll the bike.

As an alternative to the S-A hybrid hub, what parts should I get to mount a double chainring (clamp, derailleur, shifter, crankset, cassette, derailleur)?