I'm testing this out but I don't know why I never thought of doing this before.
I created a MIDI FX plug-in that creates a virtual port when I can send to the virtual port to redirect to another track.
What's cool about this is, the flow for the MIDI FX goes down the chain to a AU Instrument, not an External Instrument using IAC.
I can redirect anywhere in the MIDI FX chain as well, it doesn't have to be the last MIDI FX in the chain.