The entity setup from pd_waterlog. Features two control points, one chosen randomly at the start after which the points alternate, along with the trapdoor mechanisms. They're quite complicated and feature a bunch of different fallbacks to keep players from getting stuck.
The central platform in the prefab contains all the logic for PD, as well as @Egan's dynamic respawn time mechanism, and the actual alternating point logic. Just use those if you want that and don't want the trapdoors.
If you want to use the trapdoors:
Point A features mechanisms for clearing buildings and un-stucking players that sometimes get shoved into the floor when the doors open.
Point B features the same things, but also launches players under the point up onto the point when the doors close and kills players that are under the point when the doors open.
Based off of Egan's PD prefab!