Hi,
I'm not sure what you mean by 'metadata for all possible objects'. Is it a cache where the users can put arbitrary objects and retrieve them later?
There is no direct caching support in vRO scripting. Some of the plug-ins have their own simple cache, like DynamicTypes' DynamicTypesManager#getFromCache/putInCache scripting methods.
One option that I haven't tried yet but that should work is this unofficial plug-in - GitHub - dimitrovvlado/o11n-plugin-cache: Cache plug-in for vRealize Orchestrator
