He wasn't asking for it to be included in the translation patch, just if it was possible at all.
The answer is yes, it's possible, but for legal reasons, it would have to require the user to own the psp version of the game. I don't think that a sprite exchange and translation would be able to co-exist without both being designed together though.
I'm sure there are many reasons Cless isn't going to make his translation use the PSP sprites, but the combination of legal requirements and not wanting to make everyone who uses his patch have a copy of both the psx game AND the psp game should be reason enough

TBH, I prefer the psx sprites anyways, and I'm sure I'm not the only one.
Could someone possibly make a patch to Cless's patch that exchanges the sprites? Perhaps, I don't really know the answer to that one.