Let's see if these mutators could be made with Haskell programming language, somehow; and/or just some general way in some mathematical category of CV mutators made up for this purpose (and you can see what are functors, monads, comonads, etc applying to).
In both cases, and in the mathematics in general, the NIL (identity) mutator should in fact be called the mutator, and it may form a monoid (if some mutators may make the game that some other mutators are not applicable to, though, then it may form a category but not a monoid).
If it is a category as above, and the objects describe features which are compatible with certain mutators, there might be an endofunctor to specify what applies to others too, and it might be a monad too (if it can be lifted into the set of additional features while keeping the same game, for example). In such case possibly even the games becoming mutators, being a morphism from a "null object" (meaning no features apply, so you have no game at all), to the object of their features.
Let's see if these mutators could be made with Haskell programming language, somehow; and/or just some general way in some mathematical category of CV mutators made up for this purpose (and you can see what are functors, monads, comonads, etc applying to).
In both cases, and in the mathematics in general, the NIL (identity) mutator should in fact be called the mutator, and it may form a monoid (if some mutators may make the game that some other mutators are not applicable to, though, then it may form a category but not a monoid).
If it is a category as above, and the objects describe features which are compatible with certain mutators, there might be an endofunctor to specify what applies to others too, and it might be a monad too (if it can be lifted into the set of additional features while keeping the same game, for example). In such case possibly even the games becoming mutators, being a morphism from a "null object" (meaning no features apply, so you have no game at all), to the object of their features.