Empire has deep synergy shared between as well as Phoenix do so mixing them up makes them just weaker I think. In an Empire squad I'd only run Kanan or Chopper as 2nd tank. Prefering Kanan cause he can dispell, taunt and attack on one move also counter with offence down in his basic. Which is never bad in current rebel meta. Chopper cause he is fast and can take beating, maybe stun R2 if lucky.
Empire team does not have that many debuff dispelling. But even then I'd replace Kanan with GK as soon as I'd have him.
But adding empire to phoenix squad, meh. Only Thrawn maybe, but to replace who, dunno.