The idea is interesting and from there can be created many other features.
For example: usually all players room are invaded by a NPC invader who just spawn in one of the exits of the room, why not create a less menancing structure like this to create a "mini-base" to the invaders. Will be interesting to find and take down that base, obviously that will not happen on main world but will be very interesting to add it to a local server for those ones who want to improve their code or just have fun playing with friends in a PvE style.
That's already happening but with full AI's from steam workshop. (And there's entire player's like base to fight, that's like a some sort of PvP against the AI, since those AI's was made by players. Don't get me wrong, those AI's some times can be more challenging than a siege to this stronghold.)
If you go through that line, you'll find a lot of suggestions for the PvE environment to the game.