at the moment... afair...
'handlers' are static 'case' with hardcoded params... so it's possible but not in any extensible way...
('methods' afaik are inline within each handler so even less extensible and these are the core of what watchcat does)
(fwiw... if your implementation gets a more generic name 'watchcatNG, link-actions' or something like that... i'm willing to fork/pr or whatever and add some extensibility samples to it if you are interested but that's totally up to you... like i said... your fork with the single dedicated task does have it's advantages...)