It should be possible to get chewie even if you do not have Bossk et al.... I suppose you do need Delgar for the upper tiers but not the lower ones.... I am trying to use a version of the below on tier 7, and I get close to killing chewie with Fetts opening move.
The tactic below is all about setting up Fett to kill chewie with excute. At tier 5 it typically will require you slowing down your Fett so they everyone else can move to set him up.
Tactics for tier 5/6. with fastest = Greedo, then IG88/Cad Bane and then Boba Fett
Boba Fett needs to be slow enough so that Raid Had gets off this team buff before Boba moves. Use Crit Damage sets with as much offense as you can. I do not know the speed required at lower tiers but likely 200 or below.
-use Greedo to remove TM from Chewie. *Chewie will gain tm when debuffed under leia lead. We want IG88/Bane to add debuffs then use fetts's excute.
-Target Chewie with basics from IG88/Cad Bane.
-Use execute to kill chew with boba fett. ****if you got lucky chewie should have 4 buffs and 2 debuffs. Meaning Execute will do 180% bonus damage, that should kill chewie, on a critical hit.***
Kill others...
You can use Fett or Delgar lead. I used Delgar myself. But Fett would have a easier time getting the frist kill under his lead.
As mentioned in other posts, Delgar is very useful for stoping R2 from using stealth to protect chewie. If you do not have Delgar you would need have Greedo faster then R2 and have him remove tm from R2 before he moves. You then need to IG-88/Bane and Fett's speed so they move right after chew does. If chew moves after IG-88/Bane add debuffs R2 will remove them on critical hits.