Your mentioning cloning to a SD card and liking puzzles is interesting. One of the two (A) N810's I bought is like new, but has a bad micro usb port. The other (B) is kinda rough, but works perfectly.

(A) Has screwed up WiMax OS and, although connects to wifi, cannot access application catalogs.

(B) Connects to wifi and accesses application catalogs normally..

As I cannot connect pc to tablet with usb on (A) to flash,

Is there any way to flash (A) with SD card?
or,
Is there any way to clone (B)'s OS to a SD card and use in (A) to boot from?

I haven't been able to find a disassemble guide for the N810 to fix the usb port on (A) and don't know if I would attempt to anyway.