Hi,
All things considered, if you believe you can make a Jack Mode implementation that is 1) Generic, i e, same code shared for all codecs 2) Free from regressions for the end user never touching ALSA and just running PulseAudio with GNOME/Unity UI. That includes all volume controls still working, non-existing ports should not show up, etc. 3) Bug free in other ways too ;-) 4) And do this within a kernel cycle, i e, without a few broken kernels (e g Realtek multi-IO implementation caused some regressions in 3.2 and 3.3)
...then I think you should go for it. But I would still see it as high risk. Maybe I should help testing somehow?
Then if PulseAudio doesn't support doing the retasking by default, then that's just something we have to work with in PulseAudio later on.