Just had an idea today, going to write it out now, and work on drawing it up later.

So maybe I could use a sort of linear motor to actuate the wall up and down?  The locking action at extension and retraction could just be a pair of magnets, with a magnet in the wall piece.  Then a coil of wire could induce a stronger electromagnetic field to push the wall up or down.  The 2 coils could even be wired in parallel, since ideally the electrical pulse would be short enough for the 2 fields to not interfere.  Then an additional smaller magnet could be used with a Hall effect sensor (AH1815) to indicate the wall state.

Each wall segment would then have 4 magnets, a solid state relay for the coils, the hall effect sensor, and the pair of coils.  Power rails would connect 2 voltages, a 3.3 to 5v rail for the hall effect, and a higher voltage for the relay/coils.  2 data lines, connected to matrices for pulsing the coils, and reading the state of the hall effect.

This sounds way more economical than my other ideas so far.  I'll need to start drawing up some things in CAD.   And then work on prototyping the linear actuators to see if this is possible.