@GeeKay:
I remember one group way back had developed a (inherently site-specific, I think it was just for the Korean Naver web-comic site) script-wrapper for web-comics that allowed people to load the official webcomic on it's native site, and then load just the speech bubbles and redrawn SFX and whatnot as transparent images on top of it, so that you'd get the effect of a scanlation but still needed to access the comic the official way.
Obviously that's A) more labor-intensive, B) requires competent programmers and some potential ongoing maintenance of code, and C) requires that the source material be available online in an official reader of some sort.
...In other words, not really remotely viable for most anyone's circumstances. But food for thought, maybe.
(Of course some people just post literally only the translations, in text form, but not everyone—myself included—find putting a set of those next to the comic raws to be nicely readable, at least not in an enjoyable way. ^^; )