I imagine a form of challenge where users would create their own golfing language that would specialize in a given area (like string handling or ASCII-art) and write an interpreter. After the languages were created, challenges would be revealed and the language creators had to solve each challenge using their language. They could not modify their language after the challenges were revealed. The winner would be the user with the lowest total byte count on all their languages.
The problem with this type of challenge is: how do you stop people from creating a language that is just a trivial substitution of an existing one? For example, I could just change Jelly's encoding to ASCII (And use unprintable characters) and call it a new language. The only solution I can see to this problem is to have it be a popularity-contest, but that's not compatible with the original winning criterion (shortest total code for all the challenges).
Could these types of challenges exist? Are there any other potential problems with this type of challenge and how could they be fixed?