Not sure you can call Chaze squishy when Baze is not only a tank, but adds 20% bonus health to both of them, taunts whenever Chirrut falls below 100% health, and gains health during each and every character's turn in addition to all the hots from the beginning of their turn.
Chirrut can hit pretty hard, especially with his special. Baze not hit as much, but his AoE special does bonus damage against Empire and non-buffed enemies (so twice against non-buffed Empire), and that can go along ways.
The other benefit to chaze is that the whole point of a zeta Jyn lead is to get lots of buffs to restore protection, which Chirrut passes around.
That being said, none of this is counter to the current meta. Unless you happen to not have R2's 2nd zeta, all the cleanses proc tm for the enemy. Likewise your Han cleanse will give them tm.
The benefit here is Cassian's starting tenacity up, but it only applies to tanks, so unless you're running STHan lead, Baze, Old Ben, Pathfinder, Cassian, that won't help much. Chirrut's t-up could be useful, but good luck getting in before Vader.
Jyn's immunity to stun would be nice, but Vader, at least, is immune to tmr now. You could maybe still get in and whack Palp right away with truncheon strike, but then Kenobi or Sion taunts anyway. Jyn is also not immune to fracture.
Any rebels you want to run against would be raid Han and CLS, probably with CLS lead, and if you want to throw Jyn in there to have someone immune to stun, and also more tmr and a reviver, that would work. R2 is still a solid rebel toon...yoi could make this work on offense maybe, but don't expect it to be a hard counter.