Well if you wouldn't use it for the solvent (Mirage supports the epson solvents, but not much else) then I'd probably make the jump to a more fully featured RIP now instead of doing an in between step... I've personally used Colorgate, Ergosoft, Fiery, GMG, Onyx, Mirage, and I have a little bit of experience with Flexi, Caldera, MainTop, and Serendipity, and to be honest, none of them is perfect. My favorite for workflow and layout is Mirage and Ergosoft, but in terms of built in profiling and linearization Onyx and Colorgate are way more comprehensive. Ergosoft is getting better, they've been pretty good about listening to feedback. I also do a bit of contract proofing, which narrows the field to GMG, Colorgate, Fiery and Oris, the last of which I've never touched. So I'm kind of useless for a recommendation because I'm pretty stuck between a bunch of imperfect options myself.
My ideal situation is a RIP that has a client/server layout like Fiery, especially since they have clients for mac and pc, but since Fiery 7 they kind of destroyed things from a layout perspective. Most other RIPs still use a hotfolder setup which I can't stand, since every job I'm throwing at it needs different parameters for the kind of work I do, and simple stuff like rotating and adding crop marks can be a huge pain. Ergosoft has a client/server system, but it's very expensive to add more clients, which is super odd to me, but then it also has the easiest layout and nesting options, much like Mirage.
It's been long enough since I've used Caldera that I honestly don't remember how layout worked, but I do remember it not feeling as simple in a drag-and-drop way as I wanted it to be. Maybe they've changed things by now. I'd try to demo a few things and see what you like working with, and generally speaking I'd kgive up on the RIP being mac-native if you really want any other options besides Caldera.
