I really don't get the folks who are confused or displeased by Amilyn and Rose being picked as the characters to include.
TLJ is structured as four interwoven character arcs for our four main kids. Rey, Finn, Poe, and Kylo. These are our four most important characters. And all of them have a character in the game already, even if Poe's is kinda crummy.
Each of our main kids has a single primary support character who is the center of their character arc. Luke, Rose, Amilyn, and Snoke, respectively. They are the pillars of this movie's structure while our main kids flail about. They are the next four most important characters in the movie. Of those, there's no doubt there are plans on what to do with Luke. Despite his limited screentime, Snoke is still the big bad dark side dude and leader of the First Order, so he's way in legendary territory. Obvious choices are the other two pillars, Amilyn and Rose.
After that, you have the secondary support characters for a couple arcs. Leia and DJ. Then you have the peripheral supporting cast. Hux, Paige, Phasma, BB-9E, et cetera.
If there are two characters to be released as named marquee characters for this movie, Amilyn and Rose are the clearest choices, since out of our primary supporting characters for this movie, the other two are probably gonna be some sort of event unto themselves.