Lots of good conversation, here. Thanks, everyone.
To clarify one summation that Steve mentioned regarding my unrestriction position: I believe that each of the four cards we seriously discussed could be unrestricted, but not all at once. Multiple unrestrictions is just as dangerous and problematic as multiple restrictions. Here's the order I would do them in, given the choice:
I know that Library carries certain risks. I don't believe such risks would result in any sort of synonym for "ruination" of the format. Some people - possibly many - might not like the result. <- This statement describes every Vintage metagame I have ever been a part of. As such, I don't consider it a primary reason for inaction.
No, I've not tested any of these proposals. It would be a fun exercise, but too time-consuming and ultimately fruitless, for reasons already discussed.
Thanks, everyone, for listening and for being so passionate about the format!