I'm hesitant, but here is an idea which needs tightening and breadth. I want to create a roguelike that has basically no skills or attributes. Instead, skills will be weapon/armor-based, and improvements will be lateral shifts instead of direct upgrades. Breakdown:
Weapons:
-Weapons can belong to any number of classes - i.e., a baseball bat would be MELEE, BLUNT, CLUB, and SPORTS
-Wielding a weapon would give you access to its special skill - i.e., a baseball bat would auto-parry thrown weapons like rocks and grenades
-Using the weapon would give you experience in that skill, and once you "level up" you can then use that skill with any related weapon, defined by the class of the skill - i.e., the baseball bat's auto-parry could be used by any other CLUB weapon
-If a weapon isn't distinct enough to warrant its own skill, it won't get included. There could be multiple baseball bats, but I want each one to be distinct in both its combat properties and its special skill. Skill overlap might be acceptable in rare circumstances.
-Potentially, cross-training between related weapons should go faster. That way the player is compelled to focus on one quasi-subset of weapons.
Armor:
-This would work similar to weapons. Armor has associated skills which are learned when "used," whether that means wearing it for a certain amount of time, or taking damage, etc.
-Armor would appear in sets, kind of like complete costumes. Or maybe not. I'm leaning towards the former for simplicity.
-Lootable from the appropriate monster type - baseball uniform from baseball player etc. There could be related armors, like baseball uniform, baseball coach, umpire; with the same rules about being distinct enough to warrant the variety.
Levels:
-Each level (or set of levels) would have a theme, a setting, etc. Pirates wielding lightsabers and snowman with frickin' lasers in the alleys of a prohibition-era city should be possible. I'm not going for consistency or randomness here, just that pure chaos in the middle.
-Special "vault" levels would let the player store any particularly nice items they came out with. This may be persistent between games, so you can start with a special load-out.
-The goals of levels could vary, so it doens't become a "race to the finish" scenario.
Inventory:
-Minimal. Carrying more than a few weapons should be discouraged. Ammo for different weapon types will be tough to handle, so there may be some abstract types like "machine gun ammo" and "rifle ammo." Recovery items should be themed appropriate to the level scrounged from.
Overall philosophy:
-Rule of three would probably be best. Three enemy types per theme, three weapon/armor variations, etc. This wouldn't be so much a rule as a guideline - if I can't think of three ideas, I probably haven't developed that idea enough, and if I can't par something down to three ideas, then I should either make some cuts or break it down into more categories.
-The game should be fast and fun. That's not to say that playing a stealth character or a sniper should be discouraged, just that every playstyle should be facilitated and not suffer from additional complexities. Major inspiration here is DoomRL.
-Magic isn't totally out, but I can't think of a good way to implement it without breaking other design philosophy. Help?
-Difficulty will hopefully be dynamic, scaling to how well the player is doing. This would take some advanced algorithms, but sound like fun to implement.
-Things like counter attacks should be more interesting, with different ways to redirect combat based upon weapon and armor type.
So that's all I can think of right now. I think it has potential, but there are a lot of mechanics which I am clearly divided on. Anything you could suggest, whether it be overarching design goals or simply weapon/armor skills, would be appreciated.