Although this doesn't address the smashTV aspect - an option would be to use your existing CP and hang off some USB controllers. I realize the drawbacks, but thought I'd mention it in case you hadn't thought of it.
Ok - so you wanted to know about your joystick layout. It all looks good, but I have a concern regarding the angling of the joystick. Which direction will be up? Some people want to push towards the monitor to be up while others want to go with the angle of the buttons. If it were mine, I'd probably make it as wide as I had to and keep the controls straight on to the monitor. Thats me though, I prefer being head on to the monitor.