I know some of the recruiters at my employer, various teams have started testing and hiring multiple vacancies off of a single job ad which is kept open for longer. To an external person it's odd because the assumption is one ad = one vacancy, but company policies and processing speed makes them try odd things to be able to hire what they need.

So while your idea is nice it wouldn't work because not every company lhas the same recruitment process, frontend or backend (visible to the candidate vs workable for the recruitment teams)