I think you can go ahead with GC EAD. When you leave your employer, your H1B will also be gone. If GC takes time and EAD renewal also takes time, you can always raise service request and tell them your situation. There should not be any issue getting it renewed. Even H1B is getting tougher these days if you are not working with client.
If I were you, I would do that. But, this is just my personal view and would not be responsible if it brings any complication in your case