Understood. There are no wrong answers.
I would get another 0Coast then and then skiff to augment it. I wouldn't put the 0Coast in a rack since rackspace is expensive. You know the architecture of the 0Coast, it has the sounds that you want... go for it. You're going to get a different sound out of this set-up than your 0Coast, even if it's the same manufacturer.
You may also want to check out Expert Sleepers FH2 as your MIDI interface instead of Yarns. It connects directly via USB and all 8 outputs can out put CV, gates, and triggers/clocks. Pair that with the 0Coast and you've got the core of your system right there (assuming you want to go all CV and gates). Then augment it with anything else you want. I believe the 0Coast will take MIDI-Clock in, but I don't know if it will output clock. Don't underestimate the need for clock in your future rack.
Bottom-line, do what's best for you and take any advice (especially mine) with a grain of salt. I'd look on eBay for a second-hand 0Coast and get the sounds I've been missing and then build from there.