I'm using PD and Jack on OSX.

Is there any way I can use some sort of PD external to control the Patching/Routing of my jack server? I'm using PD to send OSC signals to control SooperLooper, a looping system that runs on jack, and I'd like to be able to use PD to control which of my DAC inputs go to each loop. I've only got two inputs, but I loop them separately and it would be nice to be able to have setups like... four loops from input one and two loops from input two switching to two loops from input one and six loops from input two without having to have ten total loops, all routed ahead of time, with several loops taking up audio processing power without actually being in use at any given time.

Can I send commands to jack (perhaps OSC?) from within PD like "route system input one to SooperLooper input 4" with some sort of object?

Does anyone else think it would be useful to control audio routing within PD?

hmmm, you could try doing the routing directly from PD. Assign the system input to PD, then assign 4 PD output to 4 SooperLooper inputs. Then it's a matter of controlling which system input goes to which SooperLooper input through PD.

Well, this is a good idea, and will probably will be what I do if all else fails, but it still leaves me the problem that when SooperLooper creates/adds loops, it registers/unregisters them with Jack, and when an input or output is unregistered from jack it loses its routing, and doesn't regain it when the same input or output is registered again, so if I plan to add/remove loops, I would have to manually do the routing each time (which wouldn't be a problem if PD could send Jack messages to make it route properly).

This solution also adds to the number of signals coming in and out of Jack, which will affect processing time needs, and in a live looping situation, I'm trying to get away with the bare minimum of latency buffering.

Granted I've never done it but I believe you can run every Jack function from the command line. It should just be a matter of researching the correct format for the commands and having PD send them out using [shell].

Sweet.
I'm using shell to invoke jack_lsp, jack_connect, and jack_disconnect.

Works like a charm.