U.S. humanities professors: Can you get back into academia if you leave?
Speaking as humanistic social scientist at an R1 (but who has also taught at small liberal arts colleges), I would say it would be next to impossible.

There is an absolute surfeit of stellar recent PhDs in the humanities. Any position that opens up will get 200+ hungry applicants. Why hire at the associate or full level if you can get a stellar assistant at a quarter of the cost.

Furthermore, if a senior position did open up and a search committee were to look at your CV, I would think they might wonder whether you left academia because: 1) you were pushed out (sexual harassment? Title IX violation?); 2) were burnt out of teaching; or, 3) something else unmentionable. If you left because you hated academia, why are you trying to get back in? Academic hiring is risk adverse because of the stakes of tenure. 

However, as an alternative, you might be a candidate for some peri-academic positions such as the director of an institute, dean of student affairs, etc.

tl;dr: Talk to your provost or dean or chair about taking an unpaid leave of absence that retains your tenured position.