I read up a little on the Pro-3 and its CV outs. It has 3 CV outs and a dedicated gate out. Have you been using them with your Z-DSP to modulate any of its settings? The Pro-3 also has an internal sequencer.
While having your sequencer in your Pro-3 is not the most optimum solution, it's a great starting point... especially since it can reach your rack through the CV and gate outputs.
If you have the patch cords, I would definitely start modulating that Z-DSP along with the Pro-3. The CV outs can be assigned to just about anything... so get wicked with it.
I know the end goal is to have a self-contained system. But don't overlook what you have as a good bench to get some experience. You could save a bit of money upfront using the Pro-3 instead of your Eloquencer. Get it eventually. But it's always best to be in a position to add more modules over time rather than everything at once and hope for the best.
My favorite VCA is the Intellijel Quad VCA. It covers almost all of the bases: it can do linear, exponential, as well as act as a simple mixer. I'm getting a little confused as to where you're at in the build because your rack doesn't match what's posted here. Seems that you already put one in there. :)
But definitely read up on the Pro-3 and that CV... nice synth by the way.