Other thought: From a nearby thread, this was posted. It's a pigtail version of the mini-B <--> female A adapter you offer now, and should be susceptible to the same rip-open, solder, and re-close mod. (I assume it's not OTG already, though Birick made no mention of software...) It won't (semi-?)rigidly hold a thumb-drive behind the Nokia, but it's probably the closest thing economically attainable.

The cable might also make a y-cable power-injection setup easier to make; it sounded as if you're thinking of adding that?

BTW, I'm still waiting to make my second order. (First order was before you had hubs, ethernet, etc. up.) I'm equipping a second tablet, for my sister, so I'll be watching to see the new stuff. She's not back in the US till July, so I'll wait a while and see what you come up with for a while before I order. I'm not quite getting one of everything, but it's close...

@Qole:
Maybe the keyboard doesn't mess with power negotiations, even though it uses a little more. But it could also be an issue with start-up current; current can actually peak before negotiation, and the device is gonna negotiate for operating power. So on really low-current sources, failure from the get-go. But with a decent current source (or maybe just a big fat capacitor added), it gets started, and is then fine with no extra power.