Rumble - Ult Changes

One of the main drawbacks for Rumble in a comp can be his lack of CC, which can be seen on motst of hit kit. i was thinking maybe on his ult instead of a slow it could have a grounded effect (Like Cass Miasma, where they cannot dash out of it or flash). I feel like it might be a good change. but dont know how it would affect his balance. So it would be nice for some feedback