A dedicated mixer module is where you should go. The quad VCA is great. But using it as a mixer AND a VCA at the same time is pretty limited. You can't adjust volume levels without opening the bias or sacrificing a VCA as an attenuator then plugged into another VCA to shape a volume envelope. I would think as the ability to mix as an EXTRA functionality and not a core. In my experience it's an either/or proposition.
I use a Quadratt 1U mixer/attenuverter for simple mixing duties. The Quadratt can be used for that, or individual attenuverting. But any small, monophonic mixer that's DC coupled will work if you don't have 1U rails in your system.
Keep the Quad VCA unless space is an issue. A 2HP Mix for $100 should do the trick... and it's 2HP. I don't like the knobs on 2HP stuff. But for this purpose, they are fine. It's generally a set-and-forget thing.
You may want to add a couple of linear VCAs... here's a dual set for $100.
https://www.modulargrid.net/e/arcus-audio-dual-lin-exp-vca
So for $200 and 4HP you have a small utility mixer and a couple of linear VCAs... (that do exponential as well).