Well, you're not entirely wrong. Lots of NOACs without cart slots had off-the-shelf flash RAM in them (but good luck desoldering the chip and re-flashing it.)
I'm sure you could hack one of those flash-NOACs to have an input for those USB flash sticks... If I ever get my hands on one of those suckers I'll try.
Dr. Gregory House wrote:Good lord, are you having a bowel movement or a baby?
It might be possible, but it'd be ridiculous to try. You'd have to cleanly sever a bunch of traces on the board and wire them properly to the NES. And that's assuming all the traces you'd need are actually on the board. I'd be inclined to say "hell no" except then someone would take it as a challenge and hack a board to bits just to say they did it.
So, I'll simply say "Don't bother."