PsGroove via PSP ~ Why not, etc?

Sorry; I know this question most likely stems from a lack of information, but why can't we use a modded PSP to perform the PsGroove exploit?

I guess, the few real questions I have deal with what's really going on at the hardware level. Considering that the PsGroove is based on a programmable usb key, couldn't we get the PSP to fake it at runtime (more or less)?

Well... The real questions, which probably show my painful lack of understanding:

1) Is there some technical limitation that keeps a fully modded PSP from being used for the exploit?

2) Is there any realistic possibility of this being done in the future (technical limitations or not)?

its on the work.