I know what you guys mean with low humidity being tough to work with, I do some charcuterie work at home, and we commonly see relative humidity well below 20% most of the winter. I have set up a drying chamber (drying chamber is a misnomer because the humidity is kept around 70%-85%) to create a more suitable micro-climate for aging my sausages. have you considered trying that for your dough aging?
Anyways, I have used a pan filled with heavily salted water to keep the humidity up. I piled salt in a plastic tub, and covered it with water, if the humidity gets too high, the salt sucks the moisture back in, if the humidity gets too low, it releases the water into the air.
Could you use a humidifying gel-pack similar to what is used in cigar humidors?
or take a defunct refrigerator or another seal-able cabinet, then add a cool-mist humidifier to the bottom of it with a line-voltage humidistat and a hygrometer to solve this problem?www.sausagemaking.org
has several threads on how to build a chamber for aging dry-cured meats, maybe we could snag some idea's from that forum? it is based in the UK, but it has plenty of US members with leads to where you can get supplies here in the US too.
You could even use a working fridge, and use a line-voltage thermostat to control your temperature perfectly too, a control unit with humidity and temperature controls are under $200.00USD, but I guess it all depends on what it is worth to have workable dough.
I plan to do exactly this for my dough fermenting chamber at the restaurant. that way i am not compromising, I get the environment I want.