Your throttle connection to the tube is essentially a cam of sorts so theoretically adding material and notching it back out for the cable to rest inside should work. However I'm doubtful because any throttle I've seen is sensitive and it's tight quarters inside of the housing-probably not enough room to do that.
Motion pro is the way to go most likely. They make some awesome products but beware of the guy that answers the phone there - he's a bit short. Knows his stuff, just not a lot of patience.
Why do you want to do this, anyhow?