Hi Alex,
I submitted a patch in May [check the archives if you're interested] which lets you the "locate" functionality of jack_transport from pd, this lets you seek anywhere, |locate 0( seems to do what your rewind does. I didn't have any response from the author about it.
That sounds great! I wish I had searched better (or maybe asked here first). I think |locate 0( is better and more general, and yes ability to seek is also very useful. Btw will this get at least into the Extended version for Linux? I'm sure it's really useful form many users.
Bests, Lorenzo