Don't dispair. If you approach the subject from a theoretical angle (i.e. "Wouldn't it be cool if...?"), you might trigger something in someone's brain that could lead to something great. Just don't come off like "hay guise if j00 mak a hax0r 4 me ill put ur name in da kredutz lol".
Personally, if I can come up with a good enough concept, it's all but assured that I'll invest the time/effort/energy into making it a reality. I have to assume there are others out there who operate the same way. Now, where is it written that we (respectively) have to personally come up with such concepts? In early 2004, I amused myself with the notion of a hacked
SMB1 that parodied the then-recent Catholic Church sex scandals. But if someone had posed the concept to me a day/week/hour before I thought of it myself, it would still maintain its objective intrinsic value. And I still would've spent three years creating
this.
Also, feel free to advertise your services as a creative consultant. I can't tell you how many times I've been in the middle of a hot project, but for the life of me couldn't figure out how to replace some object in the original game in order to make it fit with the theme of the hack. As an example, I've had a terrorist-themed hack of Zelda II on the back-burner for a few years now. The humanoid enemies (Moblins, Goriyas, those Axegator things, etc.) will all be replaced with your typical, run-of-the-mill ululating splodeydoper. But I needed some way of replacing the smaller enemies (Bots, Birds, Spiders, etc.)
After agonizing over it for several days, a friend suggested I replace the lesser enemies with stuff that we're no longer allowed to bring onto airplanes
because of terrorism. Sheer brilliance. Now you have to fend off toothbrushes, dental floss and tiny eyeglass screwdrivers, in addition to Akmed bin DurkaDurka.