I've been of the opinion that the classic rogue 1 team with R2 subbed in for Baze would be extremely righteous. R2's auto cleanse and smoke screen fill in 2 of K2's 3 big holes making him a very hard tank to get past. Baze isn't that great really. He's the weakest part of the traditional Rogue 1 squad by far.
You were talking about Captain han for Chirrut too, but that isn't a good idea if you plan on keeping K2 as your tank. Chirrut's HoT on damage is practically essential to K2's continued effectiveness in that squad for 3 reasons:
1. It heals him automatically, which is practically needed for a tank these days. Captain Han is only on his turn and only if he's full.
2. With the Jyn lead not only is he recovering health every time he gets hit, he is recovering protection too because Chirrut heals him through buffs every time he gets hit, which means an extra 5% protection for him
3. It assures he taunts, as he has 100% chance to taunt while buffed, only 75% chance to taunt when not buffed.
With R2 and Chirrut combined under a Jyn lead, CLS can use his special move on K2 and he will just counter, cleanse the buff immunity, and gain a HoT to ensure that he is taunting, while regaining 10%-15% protection for the 2-3 buffs he will get (the 75% taunt can still proc in addition to the buff related taunt giving him 2 buffs). Then smoke screen forces focus on K2, so even if he gets dazed or fractured he will still have to be attacked by the enemy.
So that's my opinion. Jyn lead could be quite good still, but requires dumping that waste of space Baze for the amazing R2.