Thank you for all the suggestions.

I admit that I hadn't even considered electronic, and honestly, probably won't go that route. The most likely frame is the Soma San Marcos because it's one of the few I can find where the geometry doesn't get really funky on the smallest frame sizes. Electronic shifting on a Petersen-designed frame would probably cause a tear in the space-time continuum.

Does Gevenalle help here? I've read some people complain that the long sweep of the shifters is actually more awkward with the Gevenalle than STI-style, though the motion for a single rear shift is smaller. If the RL340 and 341 blades were identical - which I don't think they are, though I can try to find out - it might be possible to splice together an RL341 body with Gevenalle Audax blades, since I believe they start out with an RL340.

Hadn't considered bar-tops (with thumbies), that's an interesting idea. Also did not know that the 11-speed Shimano stuff had reach adjustment and shorter throws.

Good to have some more options to consider, in any case.

Don't supposed anyone has a ride report specifically on the small version of the Microshifts?