I don't have a specific road map set down for features, I'm simply implementing what I want as I go along. The end result should be something like this :
* Randomly generated city with various districts, or a large, premade city based on a real life location. I prefer the latter. More character can be placed into the locations you create yourself.
* Dynamic AI that adhere to schedules (work,the eat, sleep and so on)
* Night and day with lighting changes to reflect the time.
* Realistic line of sight, realistic stealth and lighting.
* Starting house \ apartment for the player and real estate to buy.
* Regular jobs for income support (or simply steal from your victims or, hell, live like a hobo)
* Hunger and various edible (and not so edible) foods. Cooking.
* Multiple attacks for each weapon (edge, point & blunt for a knife, as an example)
* Trophies. Body parts, fluids and possessions. Place drops of blood on slides if you want.
* Fleshed out mental states, traits and psychological profiles. Experience hallucinations, insomnia, black outs, fits of rage and other conditions. Have traits that automatically perform actions against the players will -- a psychotic who randomly takes off his clothes and runs naked through the streets.
* Drug and alcohol abuse, which ties into mental states and can change your psychological profile.
* Realistic justice system. Get life or the chair for serious crimes, jail time or community service for lesser.
* Realistic evidence system. Police gather evidence and actively seek to find you.
* Disguise's and evidence prevention items. Wear protective plastic suits and masks during messy jobs to avoid spraying blood on your clothes and skin. Place sheets of plastic around the surroundings to reduce the risk of evidence exposure, Dexter style.
* The ability to kidnap characters and take them to any location. Keep them prisoner.
* Reports on the television and newspaper concerning your crimes. Media and public hysteria.
* Join various factions. Become a mob hitman, a crime scene analyst who uses his departments assets to track murderers (hmmm...), a dirty cop, a psychologist who eats his patients. So on and so forth.
Most of those features are a LONG way away though.
Edit : No, no no! Hands off the cookie jar. I'll release it when it's in a state that doesn't drive me to fits of rage.