>> So this existing "work around" for the bridge chip of the R500 cards doesn't
>> work with the bridge chip of the R600 (or R700) cards?

> I have no idea, Andreas. [...] I've never looked into bridge chip functionality
> [...]. I don't even know if they are the same components (on the R500, R600,
> and R700 cards).

If they are (or if they aren't, but the existing "work around" for the bridge chip of the R500 cards also works with the bridge chip of the R600 (or R700) cards), future extra work to support AGP variants of R600 (or R700) cards shouldn't be required.
Searching the WWW I've found that the bridge chip has kept the same name (RIALTO, as mentioned by me 5½ years ago) throughout all card generations up to and including R700 cards. Of course, it could still be incompatible revisions of the same chip or even completely different chips despite the same name being communicated externally.