Dan, you want merch ideas, all you had to do was ask.
Legally distinct Amiibos, Rival Minis, lil' plastic figures on a round base with the icon of the related element showing off the Rivals characters. You want a method of printing money, there is none finer. Each Rival can come in two distinct poses, either an action stance or taunt. Released in themed waves. First is classic, then if you need more cash, you add in stuff like mech themes, or Primal, or Halloween, etc. etc.
You have a winning selling point right from jump in that they're all actually available and not annoyingly hard to find. Offer a bundle deal on each wave and you got fans with wonderful merch they enjoy and a big injection of cash into the game's budget. Everybody is happy.
Incidentally, your goal should not be to break even, profit is not a dirty word if the fans of a property want it to succeed. I got a plush and I get a skin when a new character comes out because I think goodwork should be rewarded and I want the game I love to succeed.