Currently Mapping browser panel can only do 2 things: Map any available parameter or action to a CC or key shortcut, and edit established mappings in terms of behavior (or delete them).
What would be useful, is ability to manually add or edit the CC numbers in the mappings browser panel, as well as changing midi port they belong to, to make it quicker and easier to assign different controllers in certain situations. And so you don’t have to delete mappings to re-assign them to a different controller.
How does this feature fit in Bitwig as a product?
Just an improvement on already existing functionality.
Could it be implemented using Bitwig components or APIs, without Bitwig team’s support?
Not really, controller scripts are not something regular user can create, while mappings panel is a basic feature, that exist to create specific bindings for the project.