My thoughts on this (in approx order of UFC's probable desirability) :
1) Adesanya vs Dricus (title fight)
2) Dricus vs Strickland II (title fight)
3) Michael Chandler vs Poirier II at 165lbs title fight.
3) Khamzat vs Strickland (if Khamzat can actually fight in USA..)
3) Pereira vs.... Someone, maybe at 205, maybe HW (title fight if 205lbs)
4) Nate Diaz vs someone....
The rumors about 165lbs and 175lbs divisions are interesting. No idea if there's anything to that.
I can possibly see Chandler (a UFC favored fighter) fighting on the card if he and UFC are tired of waiting for you-know-who.
It could be that UFC deliberately put Chandler on the UFC 300 card as a "Conor we're tired of waiting for you so Chandler gets a ufc300 fight" message.
EDIT:
That's my long shot for this card : Chandler vs Poirier II either at 155 or at 165lbs. Chandler always been a favorite of Dana's. What Chandler wants, Chandler usually gets.
And then the UFC can do McGregor vs the winner of Chandler and Poirier later in the year. Conor has history with both fighters, it's perfect.