Don't be afraid to look at a complete synth voice to start with as well. Eurorack has lots of really interesting options for things that basically could run standalone in a limited fashion, and then you just add a module or two as you go along. A Moog Mavis or a Quadrantid Swarm (just two of many options) will work out of the box and even have their own case, though they can still be racked after.
There are also lots of sound-making modules with their own built in VCAs or filters. All sorts of varieties: Plaits, 4ms Spherical Wavetable Navigator, Befaco Oneroi, Gamechanger Plasma Voice. You could pretty easily start with these and 2-3 other things (the A-143-2 and Pam's or the Mimetic) and already have a fully functioning system as long as you have something to plug it into that can take the signal.
I also feel like the Niftycase is worth a mention. It gives you 3U, 84hp with power, MIDI for up to two tracks of CV/Gate (or 5 triggers/gates depending on what you need), and a quarter inch output with two inputs. The price is very reasonable. Those cases you looked at seem nice, but if you're worried about cost and value for money, Niftycase is a potential alternative and the whole package costs about as much as most MIDI to CV modules do on their own.