First I would like to start with my own personal history on deep dungeons.
When it was first announced in HW I was like, cool, we're getting a randomized roguelite content. And at first I was fine with it, but the more I played potd the more it was clear that something is missing. But I thought it's alright, it's the first attempt, surely they will make it better next time...
So we got HoH in SB and while they did added a little bit, the core of the content was absolutely unchanged whatsoever.
In ShB they skipped deep dungeon completely despite the ronkan place being a very obvious placeholder for one, but I would guess they saw how poorly deep dungeons are performing and decided to focus on bozja instead.
Coming back in EW, a whole expansion later with promised changes, surely after such a long time they updated the content right? No... they did not.
Then in DW we got a whole presentation and promise that they are looking into deep dungeons and how to make them better. And while they did make the overall content progression better, the core content of what deep dungeon is is still 95% the same as potd... at this point I lost all hope that people in square enix even have any sort of inspiration to do anything creative with them.
Now some of you might have guessed what I mean, others are screaming into their screen "Fox! What are you talking about?!" or "Go fox yourself, they are perfect!"
What I'm talking about is that the entire content of deep dungeons is go in, kill mobs, move to next floor, kill mobs, move to next floor, kill mobs, move to next floor, and repeat until your brain cells die of boredom one by one.
Should honestly take a page from Nyzul Isle in XI not only concept but also reward structure. In Nyzul, floors are randomized and each one has a different objective to move on to the next floor. So like you would need to clear all enemies, all of one type or enemy or just one notorious monster. Everyone needs to click on a lamp or find a bunch of lamps and click on them at the same time. Or even you need to avoid a certain enemy, one that usually agros quite easily. Sometimes you even got a free floor. Then at the end there would be a big boss. We don't need an exact copy, but at least the variation in objectives made it entertaining.
A way to acquire perks, bonuses, and building up exotic, unique builds as you progress through, making for unique builds for each run would also be amazing and increase the replay value by a ton. Perhaps even acquire flaws too, but point is, having your character evolve beyond the party just collecting pomanders. Don't get me wrong, pomanders are great and should remain in a form or another, but they're the consumable/trump card part of roguelikes only. (For example you could get access to a new phantom job-like ability /passive upon completing some objectives at the lower effort level - IE reuse existing systems, or a torghast-like system enhancing some existing abilities IF the devs want to put in more dev time towards it)