Is there a way to change key bindings for just one character?

I just want to be able to use self cast + smart cast on ultimate; because, when 4 melees dive on top of me in a team fight some times I end up clicking on one of them instead of myself. It seems to favor the hit box of an enemy champion instead of your own when it over laps both champions. It would be nice for abilities that have the option to both self cast or hit other targets would allow you to just double tap the key to use the ability immediately on yourself.