This idea honestly isn't far from how raids worked back in the coil days. Your progress passed the "trash" was remembered for the week - but with the difference that only 1 person needed the checkpoint and then could act as a skip for the rest of their raid buddies.

Anyways, it seems viable enough, but I'd honestly rather see savage 4 player content. The biggest hurdle of doing 8 person hard content is organizing, and IMO that's where 24 would become especially annoying and troublesome. Especially outside of new content patches.

4 person would be much easier to organize and prone to far less disruption because one person had net issues or wife/gf aggro or some other issue.