While dredge is the poster child for "what does this do to opening hands" I think the ability to mulligan aggressively for silver bullets is likewise a little brain melty.
Leylines, major hate pieces, power, force of will...the game would change radically if you could actively go fishing for them and potentially still come away with a keepable hand.
All opinions contained in this post are simply that: opinions. They are mostly based on anecdotes and qualitative, not quantitative data.
I think there will always be a bit of a difference between the paper and digital vintage format. The aforementioned loops issues keep certain powerful deck types more or less out of MTGO (I have a fondness for bomberman, but not enough of one for the carpal tunnel). There is the cost issue- it is easier for me to shift cards around in my deck and try new things in a league or a challenge on mtgo when the cost to try new things is low. MTGO also lets me try things I'd be less inclined to put together for one of my local vintage leagues like Saheeli Oath or some horrifying Brian Kelly concoction.
I also tend to play different decks in paper than I do online. I tend more towards workshops and weird xerox decks online (or fun things like Aperture Science) while in paper I've decided to stop being an artificer and have gone back to my first love of necromancy.
Vintage is a digital format. I don't think that vintage is only a digital format. I don't think the paper and online metagames are identical, but neither are they all that far afield from one another.