Okay, well based on your use case outlined about, I would additionally suggest you hold off adding in-rack mix capacity till you know you need it. Mix modules appear (to me) overrepresented in your current build above.
BTW a few months ago I went nuts with getting in-rack mix capacity, more than I had proved I needed, and it is basically unused in my rack.
RE Stages or Quadrax+Expander, yes either of those would likely serve you well. I have Stages and love it BUT it can be hard to learn how to use without an Oscilloscope as it is very powerful and depends greatly on how it is patched. Quadrax I don't own but I've heard good things; I suspect that one might be a little more direct in usage vs. Stages. But both are good options.
Good luck, enjoy!