It looks like there are a lot of reasonably inexpensive DROs out there.
X and Y are mass-sensitive, have to move fast, and don't generally need to be super-repeatable when it comes to homing, so limit switches make lots of sense and DROs wouldn't.
Z is typically not so mass-sensitive, moves slow, but should be very repeatable for homing, especially with non-sprung beds where a head crash is extra bad.
Many DROs preserve absolute position across a power-off, and many of them speak known protocols.
I did google and site searches, but I don't see any instances of using a DRO for closed-loop Z absolute position. I would still want a limit switch as a backup, but setting an absolute origin in a DRO and then going straight to the first-layer Z height without dancing on a limit switch feels like it could be a win on a sufficiently stable machine.
Just pondering here...
Am I missing something obvious?