This is an interesting concept and not one I'd considered. I'm quite interested because I'm thinking about button and switch designs at the moment.
A button component that has a built-in option for a temporary intermediate step which is either time-based as in your example or event driven, eg. after a click, it stays in the intermediate state until some external event moves it to the final state.
I suppose you would need to allow for a similar warm-down transition as well?
Such a button could be visualised either as a traditional button or as a "switch" I think. With the switch visualisation being a horizontal or vertical pill shape as you describe.
Are there other features you would want in such a button?
And note that I would keep this distinct as a button and not a multi-way switch which is something quite different. I think that would need a different definition.
I've just been building a web component that duplicates browser console log output to the web page. But an enhanced button might be an interesting next component to work on.
