Event based architecture. I've had a lot of fun and learned much while delving into simple event based programming and I think this will be a good test of how to apply it to an interesting application. Roguelikes tend to have very messy dependancies and have an unholy number of exceptions to the rules and complex interactions so this will be a good test of how well I can make events, commands, and sagas work.
Interesting overworld. I've gotten tired of playing games that have too much uninteresting space. Long corridors, huge outdoor fields, empty room after empty room after empty room. I want small and unique spaces. Moving is so boring that some roguelikes have it automated for you. Despite all the hours I played the original Zelda as a kid I never got tired of it. Each screen had its own unique charm and character, each fit within its own little neighborhood, and each area had it's own secrets to reveal. I want that.
Random monsters. Other than the Forgotten Beasts of Dwarf Fortress, I haven't seen this implemented. I don't think I'll have DF's giant vomit monsters, just a few species with three or four random advantages each game. This should add variety like identifying potions does, except perhaps with deadlier consequences.
Dynamic quests. The more I think about it the less intimidating this seems - but that may just be my own hubris. Since it's a 7DRL I will probably only have a few quests. Getting other people to follow commands and attempt the same quests would be interesting - and it should be possible if I'm right about the connection between commands and quests.
Focusing on these means I would de-emphasize other things. There will probably be just a few simple armors, weapons, and other items. I will most likely skip magic alltogether. The game itself may not even be fun or difficult. I'm not sure what the story will be either but it should involve quests and followers. I should probably think of something soon otherwise I'll end up with just a proof of concept: a bunch of neat ideas with no theme to tie them together.
My 7 day plan:
Day 1. Hyrulian Overworld: worldgen, player controlled @
Day 2. Basic gameplay: basic creatures, basic combat, basic stats, basic items
Day 3. Monsters: randomized monsters, better creature AI, a few status effects
Day 4. Society: people, victory, basic commands
Day 5. Dynamic quests
Day 6. More content and polish....
Day 7. More content and polish....