If this follows the Chimera style ship unlock, there are only two ships that should be required.
The Imperial Tie Fighter and Slave I.
Most of the Legendary/Heroic/Ancient events stick close to the lore. Chimera required both Phoenix ships seeing as they were Thrawn's primary opponents. The same should hold true for the Falcon because the Tie Fighter is the primary opponent that the Falcon squares off against. The first dog fight in Star Wars was the Falcon versus Tie Fighters in Episode 4. In ESB, the Falcon is chased by Ties through an asteroid field. In RTJ, the Falcon and Ties duke it out in a massive fleet battle. It is the one ship that is deserving of being required for the Falcon. Slave I makes since it stalked the Falcon to Bespin in ESB. The only other ship that remotely should enter the conversation is Vader's Tie Advanced since the Falcon did engage it and its escorts in ANH to save Luke.
That all being said, I have zero problem with the third ship being required being BH since it makes sense considering what we have in game. I figure the event is going to be difficult that you would require four or five ships regardless.
I honestly don't expect Imperial Tie Fighter to be required since there is little money to be made in it. However, it would be a shame if it is not because of what it represents. The first dogfight in Star Wars history.