Something like this would make a great basis for a new type of dungeon like content, 'exploratory dungeons' or something.

Make them large, sprawling areas with different sections, hidden areas, traps, puzzles etc. And since they'd require time, and communication with your party about what you want to accomplish there, keep them out of roulette and df, have to queue manually with a group.

Since you're manually putting the party together, you can of course choose whatever composition you want, would be nice if they could make it at least a little flexible in number of people you could take in as well. Certain sections could be harder than others and require more people, ie: the main floor is meant for 3-5 people, but if you go into the crazy wizard's tower its meant for 7-8.
You could decide with your group what parts you want to do based on who you have/what jobs etc.

A different style of dungeon content, not to replace roulette, but alongside it for variety would be nice. Give people who want the old school dungeon crawl feeling something to enjoy.