we do not plan to support this feature.
The catalogues are currently deeply integrated in schema and are validated on multiple places, which provides its benefits, but may be also an issue in some scenarios, such as the one that you have, and where you would prefer a more dynamic approach.
Giving the possibility to change them dynamically would be beneficial for scenarios such as yours, but that rises lots of issues when deploying a schema in such a system.
In particular: you activate a schema. Then you add 3 new entries to an existing catalogue via REST, but they are not present in the original schema. You then add a new objecttype to schema, a new catalogue entry, and deploy the schema. What shall happen then with the entries created via REST - add the new one from schema and remove the REST-entries (maybe you dont want them anymore and that is why you deploy), or leave them (because you created them and you just want to add an objecttype and one more entry). As you can see, that creates lots of ambiguity where our code cannot make a clear and correct decision. We can add new levels of validation and but that will make the deployment process more complicated and clunky.
For this reason, we do not plan to provide the mixed approach (catalogue in schema and changeable via REST).
If you see that this highly dynamic behavior remains, it would be worth considering to switch to dynamiclists, as you have proposed.