I'm considering making a MIDI controller I/O shield for Teensy LC & 3.x. Now's the time to suggest what features it ought to have!

We pretty regularly get questions on this forum from people looking to build MIDI controllers with incredible numbers of pots, encoders and buttons. The main idea of this shield would be something moderately sized and inexpensive, but "stackable" in some way. Maybe each one would have 3 or 4 mux chips, for connecting 24 or 32 analog inputs. Tech-wise, nothing all that sophisticated. The main purpose is to keep the cost low enough that it seems like a good deal compared to trying to wire up dozens or hundreds of wires. It would also be a "known quantity" as far as analog performance, rather than the situation we get now where people end up with tons of wires connected and lots of analog noise, which is tough to troubleshoot.