Rotating climbing wall with servo-controlled pins for holds

Rotating climbing walls already exist, but as far as I can see from my research, they are a fixed set of holds on a rotating surface (by fixed I mean that they don't change within one continuous climb).

It should be possible however to make a rotating climbing wall with servo/solenoid-controlled pins for holds. These holds can come in and out of the surface, changing the configuration dynamically whilst the user is on the other side of the board. Hence the user has a continuous non-repeating climb.

The holds could be made from the same material as normal climbing holds, and could be configured with various shapes. It may be possible (and necessary) to have a door that covers the hole for the hold to retract into, so the user isn't tempted to use the entrance of the hole as a hold.