New levels every day is always nice, but that is a harder thing to do to in your kind of game as well as a game that needs to be downloaded rather than played in the browser.
But it's not really the kind of game that would work as a crossover. You COULD add a pure puzzle game, but that wouldn't really fit it TBD, though if you did it would be a much-needed way to earn creds a bit faster.
Some people may like leaderboards, like highest Outerworld level reached, highest character level, total characters unlocked etc., but not me. I like that it is a purely single player game.
Not really related to Coin Factory, but in the intrest of earning a few extra currency, you could add a daily random win. Spin the wheel, trade a random sould (not permanently) for a prize, or something. But I already made a suggestion that you liked which amounts to the same thing.
What feature from Tetris would you like to see in PUBG? It's pretty much just as daft a question!