The latest so many insane plays podcast asked folks to weigh in on what they would unrestrict and I think that's an interesting discussion to have.
I don't think the podcast tread is the best place for that because most of the podcast is a review of the newest set and this would derail conversations about that.
The existing restricted list discussion is mostly about restrictions rather than un restrictions, so I think a separate thread is warranted. As a rule for this thread I would politely ask people to do two things
Have posts mostly be about unrestriction, though if you want a paragraph talking about how you see the format in general, that's ok
Do not reply to or quote any posts or portions of posts talking about restrictions. Reply only to posts or portions of post discussing unrestriction.
If we all adhere to rule 2 this should be a meaningfuly different discussion than the other thread and it might be interesting.
To kick things off, here is how I responded to the podcast
Big fan of your show. I heard your most recent episode and you asked for thoughts on cards to unrestrict.
Personally, I think a major problem with vintage right now is that power creep in threats hasn't kept up with power creep in answers and too many strategies are shut down by overwhelming powerful answers. So my preference would be to restrict misstep, mindbreak trap, cage, and containment priest and see if that brings back storm / oath / reanimate.
But, in the spirit of your question here are some cards for unrestriction in order of how dangerous they are.
Library Of Alexandria
This is probably on most lists. Very powerful source of card advantage in a control deck that is ahead or even. It can be shut down by forcing interactions, pitch countering, or with wastes. I don't think it breaks the format, but I also don't think it really pushes hard in the directions people want.
Ad nauseum does much the same thing as bargain for one mana less. What unrestricted bargain does isn't boosting storm or bargain decks. What it does is give rector decks redundantancy so they don't lose if they randomly draw bargain. I think they are still not good enouph though.
This is one that I think is probably on fewer lists. In the old days combo was getting two cards together like illusions donate. Today most combo decks are storm style combo where you have a bunch of velocity, a few resource positive cards like rituals, and a single win condition. Two card combo decks have mostly gone away.
Modern storm style combo decks probably can't safely play consult. (Note, burning long did play consult, but back then you could wish for RFG cards, the change to excile not being wishable was a big nerf to consult compared to when it was restricted). Too much risk of removing a win condition or even their whole deck. But two card combos that play 4 of each piece would get a huge boost from consult. This could create a lot of new archetypes without putting too much additional power into existening decks.
Non artifact ramp isn't much played in vintage. Lands decks are a bit too weak to play. Exploration used to be at the cusp of playability (maybe right below), but after the printing of misstep it's clearly not strong enouph.
I think fastbond adds a lands combo deck to the format and a lands lock deck (with crucible and the new 2/3). The lands lock deck is probably naturally strong vs shops and leads to a big shakeup.
Risk is that fastbond makes draw 7 style combo too strong with too many natural turn 1 kills.
If unrestricted the balance deck would be the best deck in the format and it wouldn't be close. Any hand that can make some quick mana find balance and balance down to 2-3 cards in hand will be devastating against most deck. It's really hard to function with 2-3 cards in hand. I don't think this makes a fun metagame, but it would be very different. We would see more dredge, and a lot more free counters, and maybe even blue leyline out of shops decks to dump their hand before balance. Maybe it makes reanimate good if you expect to discard 3-4 cards before your first turn.