A complete reworking of the dungeon crawl experience (nethack, amod, etc)
-A similar story (your awesome god sent you on an awesome quest for the amulet of yendor, etc) with similar quests and goals.
-Modern graphics, dark and detailed artwork, sound effects, etc...
-In depth character creation, customization, but with similar character classes/races to the classics (wizard, valkyrie, etc.)
-Randomly generated game content. Every time.
-Hardcore mode only, no messing with saves.
-Incorporate multiplayer into the "bones" files.
-Real time gameplay instead of turnbased. (this is the biggest thing that roguelikes are missing)
-A sense of action and urgency.
Basically you are combining gameplay elements of NetHack, Diablo, and Dark/Demon's souls, into a game with infinite replayability.
Please forgive me if this makes no sense or is boring.... I suck at converying my ideas.