I think it would make sense to make Basic.t a representation of JSON whereas Safe.t could be a convenient (for those for whom integers are convenient) interpretation of it. There could even be conversion functions between those.
Though I would suggest we concentrate on releasing 2.0.0 with the current (mostly minor and hopefully not affecting too many people) breaking changes and then rethink the Basic/Safe/Raw variants for 3.0.0 (along with some maintainability updates).