Not minimal in cost, but very “minimal” in terms of footprint and having no functional excess during performance: ER-301 w/ 16n faderbank.
It is super easy to create a mixer control surface on the 16n with channels exactly tuned to your hardware needs. Limiters, EQ, feedback, preamps (only 4x gain though), etc. are available but the signal routing is up to you.
I played a collaborative improv set this week with Violet Housekid and had just enough faders for my Lyra, our two modulars, some ER-301 sample playback, and a cue output, plus send buses to use the Lyra and modular as effects (with feedback!). That cue output saved my ass by letting let me retune the synth “silently” to join in at the end of a Duet for Theremin and Lap Steel’s ongoing performance.