Pool stuff pack.

Make it a Water Park Game Pack and I'm in. Simple slides for home use, elaborate buildable slide parts to make fancy large park slides of different types and pool playgrounds (or land playgrounds; make it versatile so we can use it was we want to). Trampolines, jumping towers of different height, starter blocks, wave machines, hot tubs that goes into pools rather than sit on the ground... Without a world or even a new venue type (pool will do fine with some updates), focus could be on build objects and functional immersive gameplay.

To make pools more customizable make it possible to add stairs and platforms to pools, and add rounder edges. Make a platform that is triangle shaped (like the roof) so you can make pools with shallower and deeper ends. That could be a base game update to go along with the pack.