I have an idea for a new kind of LEGO, using new types of elements
If the idea is a new kind of part, element in plastic, you may want to take it into your own hands and try to design it in a free cad app (like Sketchup, Open SCAD, Creo Elements or something). There are people around here (like myself) who have 3d printers, and may be able to suggest or try things out. You can then see if there is a market for such Lego compatible elements - see who else is interested. 

Lego are unlikely to take these kind of risks themselves, but there are resources for people to try new things themselves.