It would start with a portal, going to a world with a wormhole to get there only via portal. Dungeon's deep and wide. Find the Amulet of Yendor! Okay, this isn't Rogue but it could resemble Rogue in its layout. Admin place--no destructing things! Except things which need to be destructed in order to pass a puzzle. Level 25 needed to enter; this is all endgame stuff, for bored people with too many plasma guns. That's the basics of the idea. Some more advanced features which tickle some people pink -- well, some people, others think are useless ideas or which will never get implemented: * Use teleporters to expand area beyond limits of POI sizes. * Complex ways to proceed, such as needing to go up again to proceed further down. * Secret areas! Everywhere! Blow that broken wall up to get the coins! And guns, don't forget the guns. * Go to dungeons inside moons, inside asteroids, stations, deep underground lava places. I want to jump over lava in Empyrion! All in system where no ships are allowed, because wormhole locks it to the portal (I know portals can do this). Except when you need to build a ship from scratch or use one available to pass a puzzle. * Regenerate loot after awhile, but only let one person in at once, until they die or are the victors. Portal closes for further entrants. * Arena areas and side-places! Maybe optional within the dungeon, and thus harder. Enter at your own risk! * Some areas might need to craft something to proceed. Make a HV to cross impossible lava, for example. Another example, maybe need to craft a space suit armor mod and waste no time doing so because the next area teleported you to a busted up station with no environment, oh boy. Resources somewhere, because the player has minimal inventory on entry, and I have seen that done with portals, before, too. * For servers, some dungeons are two-player, however that can be done. Much, much harder encounters, arena-style, buku hostiles. Didn't someone suggest an arena? * For the ultimate challenge, procedurally generated underground wormholed dungeons. Losing is fun!
One implementation of this idea could be a "Ziggurat" type structure. I remember this also in a free roguelike called Dungeon Crawl Stone Soup. The area is simply a big pile of levels, one stacked on top of each other, and the player starts at the top in the smallest room. You don't get to advance until each room is cleared. At the end is the exit, but each room also has an early exit. This could be very hard, as there are many levels and each one is bigger and thus harder than the last, in the structure. But it technically fits any player level from the first room's encounters on up to advanced players.
"Arena areas and side-places" is from Doom the Roguelike, originally. Also Jupiter Hell, now. Many places there are optional, if harder. You'll probably die, but you might need to complete at least a couple in order to get better equipment and ammo for the end fights, or some kind of key, is the idea. I know we do keys, now.
Project Eden's Rogue Start is a great example of a dungeon done up with secret areas. The game does allow stuff to be hidden and stashed, hiding behind visual effects and passages and loot you don't notice easily unless you're a Righteous Dungeon Delver.
My plan for an end game area is basically a seamless mega dungeon, IF I can pull it off without too much lag. But I may just have to use portals instead if it causes too much lag to seamlessly connect mulitple POIs.