The amount of control fields (that are always present in modules) keeps growing which limits the field names available. Introducing the underscore in the _stp field was an attempt to make them unique enough to not collide with "normal" field names people may want.  The problem there however is that it currently can't be used in the templates format class as that uses underscores to indicate marker types (e.g. _if). This can of course be changed but that would mean all templates requir...

Certain area's of JAS may need mutex to ensure correct functioning. Caching being one example (although overwrites don't matter too much) however there may be more areas where this applies...