I like the concept behind it, but I'd also like something that imo channels the feeling of one of the most enjoyable content in the game. Baldesion Arsenal. I'm talking about the actual instance itself, not the journey to get there.

I'd say have a set of Deep Dungeons that are scaled to fit the amount of players going in them. Like a set of them for four people, and a set for eight. The floors being RNG I'm not a fan of so instead have it be static, each floor has it's own layouts and hazards and takes the risk of roaming mobs into account.

I think it would be fun for the sake of progression that completing a set amount of floors (Let's say 50) with a four person, unlocks a route(or an item you can use) to enter the eight person DD. You'd then go into it either with your current party or head in for a queue and then the eight people would move through the dungeon. The risks would be heavier, maybe have some cool puzzle challenges throughout that split the party in two. They solve objectives to help the other party move forward and vice versa.

After getting through the set amount of floors in there it'll open the path to real deal, the Deepest Dungeon. Where it grows to be something around 24-56 person instance which channels the essence of BA. Treat rezzing the same way as normal DD's, but just make it scaled to match BA's elemental level system. So that way the risk is there in terms of things hitting super hard and of a timer. They could fight specific bosses, solve even crazier puzzles with that many people, but have this huge sense of unity throughout it. But the big thing would be having a normal queue system for it instead of the nightmare that was getting everyone in for BA.

To me I think making a deep dungeon (if Shadowbringers is the focus) is using the ruins of the Qitana Ravel as a good layout for it. It gives off the huge sense of adventure especially going through the main scenario there.