I think the problem with this approach comes when certain cards aren’t easily generalized. For example, I believe that Treasure Cruise and DTT both should remain restricted but it’s difficult to define a category that would include these and any other future printing. You could say “Restrict cards that draw 3 for an effective 1 mana or less cost but that doesn’t include DTT. And clearly Ancestral Visions isn’t a problem.
It almost has to be based on gameplay observations since on the surface the delve spells don’t appear to be as dominant as they are. But through gameplay it becomes obvious.
Also, times change. I think currently all the draw7s can be unrestricted and would have zero impact on the meta. There was once a time when that would be a crazy idea. Times changing gives reason to unrestrict more cards from the past. Like Necropotence, Channel, and the like probably aren’t going to be format warping like they once were. You can’t just restrict a card like Lodestone or Chalice and say “were never going back to this”, what about when Lodestone is obsolete? Or what about the period of time between “broken” and obsolete? Doesn’t Lodestone deserve to be played when he’s “just fine”?