The older crowd would have more life experiences and interesting points of view in life. Plus, a tendency to be more physically interesting! heh! (smoking his pipe)
Just think of what you would like to see and write a rough draft of it. Then go over it a time or two and then have someone review after that! Pick a funny scenario from your past. That usually works pretty well and bring it to life! The community here has people who would love to help you create a Adult/mature VN! Plus, it helps everyone out!
Honestly? I've considered this >>. I'm in the advanced stages of editing 1ne of 2wo books I've written, but I also have a list of shorter stories I could possibly turn in VN's :/ I guess I'm just uncertain because I've never coded anything and have no way of acquiring sprites for such a project :3 buuut maybe~ n_n xou do make it sound much easier than my own head does "^__^