I think the basic issue with your raid is this: most people don't like not clearing a content, regardless of rewards they might or might not be getting. It might be something you personally enjoy, but the vast majority of people (at least in this game) do not. So a content designed for frequent failure is going to be unattractive from the get-go. Especially when that failure is paired with being kicked from the instance where you have to pay a fee to get into in the first place

I also think your idea of "puggable" may be a bit different from most people's, as most use it to mean DF'able. And as we know, a hardcore raid is not DF'able in the least. Even ex Primals are hard to DF until everyone is so overgeared that mechanics cease to matter.

Personally, I would not bother to waste my time and tomes on something that has such a high risk of failure.