http://cs.joensuu.fi/~mmeri/usbraid/
You can modify the eMMC by booting Maemo (or Android/plain Linux) off of an SD card.
Backupmenu might work too (has a console), but I don't think it has the tools required to repartition the eMMC.
I don't know whether or not the standard power kernel has raid enabled, but you can just compile your own kernel to be sure.

Just try it. All this discussion about swap and whatnot won't result in any useable numbers.
Possible? Probably. Worth the trouble? No.