They'd be ok playing their account, while you play yours.
It likely wouldn't win for you, due to lack of syncrosity and coordination.

If you were to play someone elses account, you'd both be banned in fairly short order.
Arena is high scrutiny. You might get away with someone elses account in an obscure location.
You won't when everything is checked and rechecked to see how they beat your team.

I wouldn't all of your accounts, guaranteed you'll lose them eventually.
In arena, probably sooner rather then later.