A lot of people have made really awesome things here and have submitted their plans using sketch up, but many of the projects aren't sketched up. Because of whatever reason? Probably the biggest reason is they (including myself) don't know how to use it ? But I bet if members submitted their projects by sending a photo, a description of how it was built, angle of degree parallel/not parallel, material and cut lists, etc.. This might open a whole new world up for this site? Maybe not but IMHO I think more people are apt to build things if they can see a sketch up drawing and easy to understand directions etc.?
Members volunteer there plans so... I think you could easily get people to volunteer to sketch up plans for people? Just have a special page dedicated to what all is need from the builder/submitter to sketch them up. You sketch up they will come.