Two non-rotating formats - Rebalance the banned historic cards
I for one welcome Alchemy and rebalancing of cards. However I do see the many problems with cards being rebalanced in historic that you though was forever.
I'm an Azorius Control player, and of all the colors on the banned historic cards 15 of 30 are blue or white. Hitting Azorius Control really hard (Brainstorm, Memory Lapse, Teferi Time Raveler, Counterspell especially).
I suggest:
Have two non-rotating formats.
Pioneer: For those who wants it the old way. No digital only cards, no rebalancing, banning and suspending is possible.
Historic: Digital only cards allowed, rebalancing allowed, no banning (suspending is possible, if a card is insanely effecting the format, but only until rebalancing is done)
Examples of rebalances (these are probably terrible, but just to illustrate why I think its possible):
Teferi, Time Raveler: As per Mirror, Mirror event
Brainstorm: Sorcery instead of instant.
Memory Lapse: Targets only creature, instant and sorcery spells.
Counterspell: The first one you cast in the game cost {U}{U}, the following cost {1}{U}{Ü}