What determines which character can be borrowed from an ally?

For a given ally, I don't always get the same character to borrow, but it's usually one of the same two or three, and often it's the same one. It seems like it could be a random selection from among their most powerful characters. I've also read that it might be the character the ally most recently used as their leader.

I've noticed that my most recent team affects what's available. For example, if I had Chewie on my last team (for that squad) then no Chewies are available to borrow. That makes sense, in that I can't have two Chewies on my team, but they could just remove him on the squad selection and force me to replace him with someone else. Anyway, that's at least one thing that affects who can be borrowed, but is there anything else we know for sure?

Solution 1:

You can only borrow the hero that last lead your ally's party in the current game mode.

For example, if you were doing a Dark Side mission you could only borrow the leader of the team your ally used for their last Dark Side mission.

It is also true that whatever character you used as the leader in your last mission in the game mode won't appear in the list of possible allies.

Furthermore, there is a cooldown on borrowing the same hero from the same ally. The in-game hints say that it is 4 hours. Some speculate that it is possible to reset this cooldown by completing a challenge that does not allow the use of allies (such as Ability Materials, Training Droids, Credit Challenges, etc.)

Solution 2:

One other note:

The restriction on picking a hero that is currently in your team seems to only apply to the last leader you used. For example, say I had a team consisting of Lando leading, with Biggs, Luke, Chewbacca and Stormtrooper Han. While no Lando allies would appear in the list of possible allies, it is perfectly possible to find any of the other heroes and select them.

As you cant have two of the same hero, this causes the hero that is the same as the ally you've chosen being removed from your team (for that fight) and another character being put on your team automatically, based on what other characters you have available.