Fanboy said:
As long as it isn't set during world war 2, or involves some kind of warfare that is modern.
As long as it's not a straight shooter (With 'steamlined rpg elements') I wouldn't write this off completely. It would be interesting to have some sort of modern espionage game (that actually involves espionage).
Actually, while I'm on this idea, what about a game where you infiltrate a terrorist cell, with the intent of killing the leader? Only, to get closer, you have to commit terrorist actions to gain their trust (bombing, assassination, ect). However, if you fail a mission objective (or complete too many missions too well) you have to deal with the consequences of that failure / success (such as loosing the trust of allies, being uncovered, or declared a rogue agent against your country). Hell, you might even be able to throw in a conspiracy theory or two, play the faction you're out to destroy as being noble resistance fighters against an imperialist power, or you could even pull off a double cross. Set it in an open world (Either fictional, or if your shareholders have the stomach for it, the real world), add in all manner of interconnected threads of alliances, vendettas, and plots. Move away from the class-based system of earlier games, instead focusing on the development either as a jack-of-all trades, who can do whatever he needs to, or some sort of specialist who can do one job extremely well. Have your skills directly affect the results of your missions, and have the plot hinge on your ability to prove to everyone (friend and enemy) that you're out to help them. Add in a lot of RP options, and serve. And most importantly, GET RID OF ALL THE GUNPLAY. A-la Splinter Cell, gunfire should be a tool of last resort, which is going to end badly no matter if you complete your mission or not. You can focus your character on that if you wish, but reward people who can play subtly, who invest time to learn about about the inhabitants of your game world, who do their research instead of rushing in guns blazing. Make it a true RPG, not a shooter with a conversation system.
I really should write all this down somewhere.