I was thinking a lot, and had to ideas to the game. One is a lot harder, but it would worth it, and the second would be for helping newer players.
In 2020, we will have some birthdays. In February, the 50yo of heavy metal with Black Sabbath, an obvious influence for the band. More, 2020 will mark the death birthdays of 10 years of Dio (which inspired Bruce as a singer, read it in an interview, and had presented live with Bruce and Nicko) and 5 years of Lemmy (who was probably an influence too.) So, my first suggestion is to add, as a way to honour their influence and memories, some characters from them, like the Figure In Black from Black Sabbath, Murray from Dio (Holy Diver) and Snaggletooth from Motörhead. I know it's very hard, because of the copyright of the characters, but it's a tribute to all who "made" Iron Maiden possible, then maybe it can be done.
Second and a lot easier, a dungeon to alternate with Lord of Light. It's mainly to help new players to get old characters. My idea is a dungeon in the weekend, whose scenery would be always the same, but the characters not. In the two days you have all floors as a quest you never defeated. And the first time you win you get fragments of an specific character, the featured for that weekend. And winning all floors, you would receive enough fragments to win the character. Obviously, the last floor must to be extremely hard. And, if you win a floor more than once, you do NOT receive more fragments from the character, but from the main souls (rare, epic, etc.) and some rare fragments (for example, the Gauntlet old characters, in a very low rate, exemplifying, 0,5% of getting five fragments of Charlotte, and the same for the others) I know it would unbalance the game, but it's simply corrected by a price increase. And the featured character, in my idea, should by chosen every week, in a random way but without repetition for a long period of time (6 months, for example). And should be any character, except for the FF Eddie, which is from Gauntlet, the Eternity Eddie, Trooper Eddie, and the other characters we have a "simple" way to get in the game. More, the character, if a 4 star natural, would be received as a five star. With any character, I mean it need to be any, even the special edition of the characters, like Pharaoh Ramesses, Samurai Emperor, and others. For the design, it could be any Iron Maiden reference, but as a suggestion, it could be Somewhere in Time, after all, it's a way to take a character from anywhere past and bring it back, or Live after Death, because it's a way to revive some characters harder or impossible to get in any other way.
Any doubt, I'll be available to answer.