I've been thinking of things that I probably won't be able to do until I get a lot more experience (still slowly working my way through a tutorial). Right now, one of those things is the idea of a roguelike that puts the player into the role of a naturalist (those people that study nature). Just give the player a randomized world of random monsters and give them the goal of studying them, learning what they eat, observing their behavior while mating, and things like that. It seems like something that might be an interesting deviation from the usual RL.
It would need a larger focus on the AI though. In fact, the entire idea pretty much revolves around a complex AI. You wouldn't be able to just have everything that can move trying to kill the player. You would need to give them other things that they'll try to do. You'd need to have them look for food, find mates, and defend territory. Give them a hunger stat and have them look for something to eat when it reaches a certain amount. Give them an age stat and have them look for a mate when it reaches a certain amount and they aren't looking for food. Give ones that have a reason to have territory some ability to choose a room to defend when they aren't trying to find food or a mate. Have some monsters form groups while others don't. Have monsters pick and choose what to eat. Do everything you can to make them act like the complex creatures they are, whether they're rats, orcs, dragons, or moving plants.
Randomizing the monsters would also be a must for an idea like this, and I don't mean just choosing them from a list. I mean making it so that the dragons that you encounter in one playthrough will be entirely different from the dragons you encounter in another playthrough. Make it so that each type of creature that could show up would have a couple of things for it chosen at random, whether it be raw stats, special abilities, or some changes to the AI.
http://roguetemple.com/forums/index.php?topic=1769.0 has some examples of the kind of stuff I'm trying to describe here.
Another important thing for this kind of RL would be to make it so that after the random choices, a stable ecosystem would come about. Have a way to make sure that every creature would have something that it can eat. Maybe you have a way for the diets of the creatures to be adjusted according to what can kill what. Maybe you have the creatures divided up into trophic levels and have a number of creatures from each level chosen at random. Maybe you just have one to three top predators chosen, and then have the random number god decide the rest of the monsters from the lists of what previously chosen monsters eat. And you would need a replenishing source of food for whatever monsters are at the bottom of the food chain, or take away their hunger stat with the explanation that they use photosynthesis or that they eat stuff that the player character ignores.
Those above three paragraphs contain the most important things for this idea, but a few other things should be mentioned as well. A naturalist RL would probably need stealth available in it unless the player is expected to use the Steve Irwin approach to naturalism. The look command might also be used for studying monsters, and may even have the descriptions given expanded on as the player advances, providing information about the monster's stats, abilities, and AI. The ability to choose a specific monster and give it a name and/or change the character that represents it so that you can identify it more easily would be a nice idea.
It is all just an an unrealistic goal that's been distracting me for awhile now, and maybe sharing it will get it off my mind, or better yet, convince someone more competent to try using it for their own RL.