Monobook's behavior on classic infoboxes is to link to the file page (unless a method is used that forces a direct file link); lightbox AFAIK doesn't work at all on Monobook, so I don't think changing the link sitewide for just Monobook would be a problem, but I'd probably run it by the other known Monobook user if I were applying it to the skin as a whole instead of just my user JS alone, just as a courtesy and second opinion (plus they're better at code than I am as it is...). I don't think even applying it to the common JS would affect the main skin, but considering there's no change to the lightbox behavior with the portable infoboxes anyway, there's no reason to apply it anywhere except Monobook, where there is the change. XP
Thanks for the help. *goes to figure out how to do this*
(And apparently I was hungry and cranky or something earlier because now, while I'm still miffed, the irritation I feel at the issue I did contact staff over isn't leaking over into other things like this anymore. And honestly, I'd understand if I contacted them over this thing and they said no. :P)