Buff to Twitch Ultimate Idea(thanks auto correct)

I was thinking about Twitch and what makes him good. His ultimate is so game breaking and so powerful. His lane phase is pretty lackluster, but once you get through it he's a powerhouse. The problem is, without his ultimate he's pretty useless. I was thinking about champions who have similar types of ultimates who rely on this short window of power to take over. Master Yi is one that immediately came to mind as his ultimate allows him to stick to his targets. Then I thought about what makes this so good. It's how the duration is extended on a kill by a few seconds. This rewards him for making use of his ultimate and allows him to keep it going.

Maybe Twitch can have the same thing? If you get a good ult and manage to kill someone, extend the duration of the ult by a few seconds? I know the ult lasts a good amount of time already, but this is pretty much all twitch has going for him in team fights. If you extend the duration on kill or maybe even assist as well(not sure how Yi's works), then you further emphasize his strengths while keeping his weakness in tact.