How about a battery grip.
It could be L-shaped, so as to improve the handling in normal landscape orientation*, like the Olympus EM grip.
And at the top, similar to the SF-10, it could have a flash that tilts and swivels. I'd rather not see another proprietary flash mount like the old Auto 110 had, but apparently nobody has figured out how to make a Q-sized hotshoe-mounted flash that can tilt and swivel.
*I just checked the battery location on the Q and it's on the left side, so if they made a backwards-compatible accessory, I guess it would have to be a left-hand grip. Then it might as well be made out of wood.