Toolkit template string substitution

We’ve got a specific use case for toolkit template where input filenames will contain a known set of string tokens (e.g. ‘MP’, ‘BALLS’, etc…) but we want to substitute those with a target set of tokens (e.g. ‘Bg’, ‘RefBalls’, etc…) on match so our destination publish template will apply an appropriate rename. Note that we’re specifically hoping to avoid hard-coding any of these rename mappings into our applications or hooks, so the ideal scenario is being able to specify this remapping in a config and preferably in the templates directly. The template keys don’t seem to have a mechanism for doing this: We tried using choice:label pairs on the choice parameter of the stringKey, but to no avail. Has anyone successfully implemented something like this?