Sorry, maybe I am missing something, but I think there are some potential problems when deleting deprecated variables:
We can control the official CSL styles and make sure that they will update (e.g. like you indicated with a XSLT script) shortly after the schema is updated. But how can we then make sure that old CSL JSON data 1.0 can be displayed with a new CSL style 1.1?
The old data file may for example still have an
event-variable but the new style file does then only handle
event-title-variable. Then, it is up to the processor (not in our control) whether there is any mapping, or whether any alias mechanism is respected.
Or do I have some error in the argumentation here?