OK...at the other end of that spew of alphanumerics (which MG's forum didn't like very much), there's this little $25-ish mixer. 4-in, 1-out...stereo 3.5mm I/O...and PASSIVE, meaning that it needs zero power...which ALSO means that you can treat these like those inline mults that you can stick inline anywhere in a patch.
I'm still trying to get info on these, but I'm trying to do this via AliExpress which...well, it's AliExpress. Those who've been there will know what I'm talking about. The big unanswered questions are:
1) maximum voltage input allowable (presuming very low voltage loss by the circuit, I'll presume for now that there's more or less a 1:1 relationship between inputs and the output)
2) can it pass DC
3) how does it react to 3.5mm TS plugs, instead of the stereo TRS ones?
These appear to be available from several dealers on there, but by and large Nobsound seems to be the OEM source for them. Has anyone got some experience with these? If they're "modular-able", these could solve a veritable buttload of problems. Not only would they be a mixer equivalent to things like stackcables and inline mult/hubs, they also overspec the Boredbrain Splix by two extra inputs. And for those who've made the mistake of creating a build with no mixers (punishment time! get the wet noodles!), this lets you put the mixers in without...well, putting mixers in.
IF THESE WORK...let me stress that. Normally, I'd wait until I've heard back from the manufacturer, but I think it's conceivable that someone here on MG might've tinkered with these at some point. If so...well, let's hear about 'em!