Next up, also made yesterday is a USB Right Analog Stick which is attached to the PSP via a suction cup on the bottom. It could look something like the following:

Not too many problems with this one, it's quite a feasible idea, it also looks like it wouldn't cost that much, it could be bundled with a popular game, like a future GTA for PSP, and be used from then on.

I suppose having a wire loose like that may get in the way, but it's not much of a big problem. Also the suction may raise a few eyebrows, but I believe this could work, given the PSP has a flat, glossy and smooth plastic exterior it should theoritcally stick to it quite well.