A quick update: I got a lot of stuff building, no issues so far (besides the one mentioned above and already fixed), and importantly Qt4 builds for 10.6 target and with Cocoa support. This never worked on 10a190 and, AFAIK, did not work on Leopard for ppc (i.e. Cocoa). No patches were needed.
I have built QMPlay2 with the new Qt4 on 10.6.8, and crash on exiting the app is gone. GUI works, video works, YT playback works. Apparently no regressions, but at least some visible improvements.
This is yet to be verified on the generic image of 10.6.8; I am using Nvidia one on the Quad.
@educovas So far everything works great on 10.6.8 for development. (We still need to sort out Xcode CLI tools, of course, I just made some ad hoc replacements using my rebuilds with darwinbuild, AOS binaries shared here and components borrowed from 10a222 and 10a190.)