Suggestion - new Everest content - updated Realm of Legends, but with all 300 champs alphabetically.

Fight every champ in the game in 1 map.
Use the same health pools, atk ratings, game mechanics and no sp3 attacks from the defenders like the original ROL. Just a long but easy 300 fight slog.
Maybe have an alternate version with 3 (100) fight paths.

Best champs to use would be the most sustainable. Juggernaut, Nefaria, BWCV, Sinister, etc.

Call it Realm of Legends 2.
no champ restrictions
could incentivize crazy impossible objectives for MSD to show off
-beat with only 7* champs for average rewards
-beat with only 6* champs for good rewards
5*s for great, 4* insane rewards.

And make sure you can farm potions from it. Preferably lvl 4 or better potions. They need to be better than lvl 3 from the original ROL.
Kabam should also increase potion inventory limits by like 4x. Stuff is hard these days and we need more potion space.

This is what I really REALLY want. Make it hard a different way, not by making each fight harder, but by making the map longer. Take time to show off this majesty of a game. A map with every champ at this point in time.