Rengar New ult concept

According to http://www.surrenderat20.net/2016/06/red-post-collection-riot-pls-on-dev.html#4 riot doesnt like rengar's ult and I agree with this as of now. Old rengar ult was okay but now rengar seems to be able to 100-0 even when going let's say 0/8. Riot I think I found a fix to this. His new ult (IMO) should be changed to rengar selecting a target when pressing r on them or something like it , that target can't see rengar for the time of the ult and rengar can jump to this target, but solely to this target. Rengar is not stealthed , he just disappears from target's sight , the target will get an exclamation mark on their head as usual but the rest of the team would be unaffected. This would nerf rengar pretty hard , but it would probably make it so that he is more of an assassin. Assassins pick their targets, and mainly burst these targets. One thing you could make with this ult , is if you kill the target while ult is active , you can recast ult a 2nd time or get a lower cooldown on it. If this affects rengar too hard , maybe rebalance other stuff in his kit. That was all , I'm no big content or concept creator but I thought about this and thought about sharing it. Let me think what you think about my idea <3