Because the original Cachebox provider uses the CB 3 system Javaloader, and the CB LoaderService loads Cachebox before loading Wirebox, the Couchbase provider is incompatible, in its current form, with CB4.
If the CBJavaloader module is installed, a separate instance of JavaLoader can be created to load the Couchbase jars, but too many manual installation variables are required.
The loading order issues with the Couchbase provider would also be an issue with developing any future providers which might require module dependencies (i.e. MongoDB or Redis which would need the javaloader).
As the Javaloader is no longer a part of the framework, it might be best to post an EOL for the Couchbase provider and discourage development of other providers which are not 100% CFML.