I hate to say it, but he's right. People just aren't going to take you seriously without some indication that you aren't just going to use them to make a custom mod for your own enjoyment. You need not actually create a mod, but fleshing out your own mod idea would be very helpful to your cause. Sketch some pictures. Figure out how it's all going to work ahead of time. Try to understand how 'corner cases' would be solved, like what happens if you jump a ramp and your body/head hits an obstruction? What if you jump through water/lava? A well thought out and well planned idea will garner more interest than the simple application form you have there. You really don't need the form anyway! People with an interest will express it, and the rest will come from your conversation with them after that!
A powerful and compelling presentation will work wonders in MANY circumstances!