Dan, very fine results and yes, I did know you were in AU. It was late at night here as you can see, and I wanted to kid you rather than post a long answer.
I think that you have the problems ironed out. Just watch for the contrast difference. ECN is about 0.5 and regular C41 films run from 0.6 (pro films) to 0.75 (consumer films), and thus the color print materials and scanners are fooled by thinking that all negative films are C41.
As for divided developer keeping, that remains to be seen. CDs oxidize more rapidly and are trickier to stabilize. You can make a B&W concentrate that lasts years, but CD kits are known to go bad rather quickly, even as a 3 part kit.