I've been reading discussions on recent restrictions, Paradoxical Outcome, Workshop, etc. There has been a lot of talk on whether restricting, semi-restricting or unrestricting some cards would promote or kill a diverse meta.
What I don't see amidst all this discussion, although I think could be helpful for promoting a diverse and healthy meta, is a consideration of semi-semi-restricting cards, in addition to full restrictions and semi-restrictions. A semi-semi-restricted card would be allowed as a three-of or less in a deck.
Full semi-restriction is a bit extreme compared to non-restriction. There is quite a bit of difference in a card's influence over deck construction between when it is a 4-of and when it is a 2-of. When a deck has 4 of a certain card, that card has structural influence over the deck. When a deck has 2 of a certain card, that card does not have much of an influence over the structure and feel of the deck. Some of the semi-restricted cards, although powerful enough to break the game consistently when unrestricted, become just another card that might be useful to draw once in a while when semi-restricted. The decks that were centered around such cards when they were unrestricted become largely useless when they are semi-restricted.
Jokes aside, I don’t want the DCI to have to solve the metagame for us. If a card is problematic, they don’t have to figure out if it would maybe be fine as a two-of or three-of. Either the metagame can handle a card, in which case it’s allowed as a four-of, or it can’t, in which case is restricted. No micromanagement necessary.