The only problem I have with Grass/Ice is that it has a nasty SR weakness which is shared with Fire types on the team.
So instead of filling in a role, such as a spinner, it will just compete with a sweeper for a slot.
Grass/Electric also has an ice weakness, and most water types usually carry Ice type moves. So I'm not convinced its the best type combination we could use.
Not sure yet what to think about Electric/Dark....