I was told by jack experts that it is better to set the connect property on jackaudiosink to 'none' and to use a script to automatically connect in these cases. Would that work for you too?

Could you provide some details of how the script would connect gstreamer to jamin's input ports?  I have not been able to figure out how to do that.

I think if it could be done, that would work for me (though I'd still much prefer that gstreamer exported a method that allowed a choice of ports to connect to).

I also think that jack client normaly don't connect. You would use qjackctl to e.g. setup the connection.

Implementation of such an extension would not be that straight forward. You would need to implement childproxy for both jack elements, have a child for each port, implement property probe on the ports. Then the app can check the ports and set the desired target.

Closing this bug report as no further information has been provided. Please feel free to reopen this bug if you can provide the information asked for.
Thanks!

You can redirect output from selected apps to ports you want (i do that for jamin) with qjackctl and its patchbay feature. BUT the biggest problem with GStreamer is that most apps not only don't honour GS's default sink settings but also don't let you set their options manually. Even gst-play-1.0 behaves in "just sink name or GTFO" way.
Why the hell even it wouldn't get settings from GS's gconf ? Does GS 1.0 even uses 0.10's settings ? Is there a way to set default sink for GS 1.0 ?

When GS's OWN apps don't let you set its settings or reading its config file, you know you in the world of pain. Just setting your output in global GS config and having all your GS apps go where they should without per-each-app redirection would be nice and proper.