I'd personally be fine with Chumley. I'm fine with any main character making it to Duel Links.
As for the other guy wanting females for females' sake... If they're a worthwhile character, sure. But Blair's basically the only one major enough to be worth it. There is no reason why Alice or DMG should be playable, and more "worthy" characters like Jasmine or Mindy are still obviously not worthwhile
Lumis & Umbra are more major than Alice was. Alice is more on the level of someone like Johnny Steps, a single-episode throwaway character. Lumis & Umbra had actual plot relevance. They're like the anime equivalent of mini-bosses. Alice was more like a random encounter.
They should have planned them for earlier if they knew that they were going to add them. Then they could have been there to duel in the first battle city event. This just looks like they don't even know who to add and are just randomly throwing characters into the game.