Quality of Life Suggestions

1) A permanent indicator for base mana cost 
          This is information that can be quite useful for decisions that incorporate effects that are based on a cards mana cost. As it stands, the only number on a card is the amount of mana required to finish filling it with mana. If a card is partially filled, or is a support that is already on the board, the mana cost must be reasoned out with percentage fill of the arc, or not known at all in the case of supports. When using cards like Spell Queller, which can affect Vanguard supports, it is necessary to know the base mana cost of a card, which is unavailable if the support is on the board already.

2) An indicator for how much mana a card currently has in it
          Along the same vein, perhaps segment the arc based on how much mana is currently in a card? Many cards have effects based on how much mana they can drain from your hand, and if a card is partially full, you have to estimate how much mana is there based on the remaining amount and the progress of the arc.
          I clumsily MSPainted an example of what I feel would solve both these issues.

3) An indicator that a Support is disabled
          Also referencing Spell Queller here, but I've seen it disable Vanguards and Sagas (Teferi and Kami War specifically). In practice, you can see a saga not progress, and I believe a Vanguard doesn't get it's recharge shine if it's disabled, but these are very subtle hints, and are not obvious if even 100% reliable indicators. Shade it out like you do a creature that is disabled?

4) Allow disabling of cards that are disabled from another source
          I do not know if this applies to many other cards, but, Burden of Guilt will not allow you to target a card that is currently disabled by other sources. This creates a very serious issue with it's interaction with removable disables like Hixus or Suppression Bonds. If something is hexproof and is disabled by either of those cards, and I pop an activated gem of Burden of Guilt, I cannot apply that disable (which would last through the enemies turn), and this leaves me open to attack if Greg can clear those supports during their turn.

5) Permanent indicator of card ownership
          I don't know if this is intended, but using Savior of Ollenback against another deck containing that card (among other commonly used white creatures) presents a problem when it's destroyed and you're given the option of returning exiled creatures to the board. If this is intended to be a memory test/guessing game/crapshoot gamble, then yay, it's working as intended, but I think it would benefit this specific situation (along with other certain cards) to have some color/marking that indicates the "owner" of a card.