If you think this would be useful in a project you're working on, give it a try and let me know what you think!
Any intended support for collections/sets? In JQL is do ‘“foo” not in (“evil”, “silly”)’ or similar matchers over sets, like if tags are on a ticket or if tickets an in an N states
If you're talking about a query where you want "foo" to not be "evil" OR "silly", you could write 'foo != evil || foo != silly'.
There's a separate case where the value itself is an array/collection/set, in which case doing anything with that is currently unsupported. Values can only be strings, numbers, or booleans.