This is actually interesting. If an 8-man dungeon was to automatically make two 4-man parties, this could be a thing. If there are no forced cut scenes, made to be optional, give an alternative way to gear up, have an min ilv requirement, and designed correctly; 8-man dungeons could very well be new content. They could at least try it, and see how the player reaction is.
The way I see it is everyone starts up together, takes down some trash mobs and are forcibly split to engage their own set of trash mobs, and a mini boss that blocks further progression. The mini boss is basically just one mob with a high HP pool; nothing too threatening. The path splits are also random each time so neither group A or B will know exactly where they'll end up even when doing multiple runs, and on multiple splits. The paths would have to be balanced though, so big pulls would be out. We don't want to have one group waiting too long for the other. After the mini bosses, the two parties rendezvous for the actual boss which can be made to be more difficult. Two chests drop for each group similar to the three for alliance raids for each boss, and I say go ahead and put three bosses in these dungeons. Average clear time would need to be around 25-30 minutes.
I'd say to try this content out by making it an optional quest with a small storyline and a nice little reward. They were willing to make a 4-man EX with Rathalos in the collaboration event, so I see no reason to not give this a go. If they did have 8-man content like this, I would love to do it. I would also do it repeatedly if needed to work towards a mount/emotes/glamours, all of those things we just love.
