:::::Usually IGN is a good source, but that was just a blog written by a random user on their site, not something written by an editor or staff, so you can't use that link. 
 :::::The quote from Reggie in the Kotaku and Gamezone articles doesn't specifically say that the Pro Gamepad was inspired by the Gamecube controller. It just says "our controller".  In fact, the Gamezone article writer goes on to literally say "Let's just be glad Nintendo had the brains to mimic its competitors and we aren't stuck with something like the Gamecube controller.".  
 :::::So...I don't think any of these sources are useable for what you're getting at yet. If anything they're even more sources to be used for the rewording of the Pro/360 controller argument really...