Unity Save Play mode

Disadvantages

It's a brute force sort of solution. This means:

• You can't currently make exceptions to what's saved
• It'll break any references from outside the list of things to save into the list of things to save
• Makes lots of source control changes
• Breaks prefab connections
• Deselects and closes a previously selected and expanded hierarchy (not investigated)
• Can't save anything marked static, since static meshes are combined and don’t have asset files
• We've not found one in a while, but some components may not save properly

How it works

The Save Play Mode class finds all references to Save Play Mode components on exiting the game. It serializes the entire hierarchy for those objects, and on entering play mode deletes the old hierarchies and creates the new ones.