Use FOO, he is essential for FO you could say he is the engine that keeps your FO team running, he has the highes speed of any member and can pass his turn to another.
KRU is the better leader for arena compared to Phasma, hey he got an easy node now.
You want FOST as a second tank in your squad.
OG-Kylo could be replaced with FOE in the future, because he gives tm to your team and can reduce tm from the enemy+nice dmg
FOTFP could be replaced with FOSFTFP beceause hes tankier and can call to assist and stun.