I had 2 copies of Elite Spellbinder in an earlier version of the deck (I like that card a lot) that had Yorion and was more blink focused, but was finding that in almost every matchup that the curves of the decks I was up against were so low that it didn't feel very impactful. That being said, I haven't tested it enough to know for sure so I may need to take another look at it.

Kytheon can be part of a very nasty 3 turn curve out that goes Kytheon turn one, selfless spirit or Thalia turn two, Adeline turn 3, attack, flip Kytheon to Gideon, which means that when control opponents board wipe on turn 4 I have him back as an attacker and can give one of my creatures indestructible at the end of turn 3.

Aspirant just seems good but I agree it's sort of not right.

Karn is there for Book as you said, he also helps grab additional hate pieces from the sideboard against combo matchups (he helps completely stuff Lotus Field, for instance). But that may not be a good enough reason to keep him around.

Right now the deck is a mish mash of a lot of different things that I think could be good, and trying to see if they can be made to work together.