I'll Have a Chirrut Hold The Baze?

You honestly want both to run them in arena. Baze's uniques give Chirrut more health and provides the immediate taunt and a taunt whenever chirrut is taken under 100% health. Chirruts HOTs also only get applied to rebel allies so he would be the only one receiving the HOTs when he is critically hit. If you can unlock Baze and run a high starred Chirrut and 3* baze you'd be in a solid position. I'd say I wouldn't run him alone though, despite being a great character.