I had in mind something based on rng, and not something you start up with, else you just go back to the base problem where nothing happens once you're leveled up inside, you stop progressing, and just get more pomanders as you go to use on the latest, hardest floors. Pomanders can stay though for sure, they're not bad, they just fall into the consummables of the content, which is good enough as it is.
But as every rogue like I've seen, as you go, you gain some random loot, some random perks and features and it's always different. You sometimes have to choose between multiple options that are offered to you and this also generate agency and choice. And all of those perks continue to strengthen your "build" and open for cool or exotic synergies that you build up as you go and your character/party gets stronger. Lost actions and whatnot could fill that role for sure, but I'd really like having that once you're inside and getting more and more until the last floor.
Of course there is another thing a lot of rogue lites also do is to make you unlock more and more perks by playing that you then load up at the start of the next run too, that's true. Why not?