No, simply because GC isn't an optional part of ocaml's design. You can "disable" it only in the sense that you stop any frees from happening.
In order to do away with Garbage collection you'd need to completely change the type system, and while you might get a result which ends up looking a lot like ocaml, it won't be ocaml any more than ocaml is sml.
This is what Rust started out as, by the way. In my opinion, it should have stayed that way. Post-Mozilla Rust has been nothing but a gigantic disappointment.
