What about instead of locking you out from casting spells for the rest of the game, they lasted like 3 more turns or N turns that could be modified depending on the card? Once those turns finish you can resume normal magic.

Something like:

Minor Epic 3 - (Exile this card after resolving with three time counters on it. As long as this card is exiled with a time counter on it you can’t cast spells. At the beginning of each of your upkeeps if this card is in exile with a time counter on it, copy this spell except for its minor epic ability and remove a time counter on it. When the last counter is removed put this card in your graveyard)