The more I think about it, the more I am able to convince myself (which may be a good, or a bad thing): Chalice of the Void feels like it could have been the lynchpin to a good amount of the current discussions around a B&R update.
In the September 2015 B&R Update:
Workshop decks have become more and more popular. However, too many games are effectively decided by the first player's first turn. A major problem is that a turn-one Chalice of the Void for 0 deprives the opponent an opportunity to put Moxen on the battlefield. While players can adapt by not playing Moxen, the point of the format is to provide a place to play those cards. Chalice of the Void is restricted.
Since then Gush has seen a resurgence. I am going to suggest that the resurgence is driven by a glut of CMC1 spells:
Other CMC1 spells are now seeing less play, including:
Outside of Paradoxical Outcome decks, moxen usage feels like it has dropped, with many decks electing to not play a full compliment of moxen.
Since that B&R update, Eldrazi-based decks have cannibalised a portion of Workshop decks.
Applying these two points to the justification for restricting chalice, makes me question whether the restriction is still needed.
My hypothesis: *un-restricting Chalice of the Void would force Monastery Mentor - based decks to have a higher mana curve, to allow them to beat chalice on 1. Whilst not blocking mentor as a win condition, it does slow it down significantly (cantrips can be cast to grow mentor, but they are countered). The increase in the mana curve does not play nice with gush. This will cause a drop in the performance of mentor-base decks, and open space for other types of decks to emerge. That is: alleviating the need for alternate restrictions such as mentor, gush, probe, preordain, and misstep.
Historically, chalice is most often played on 0 and 1. Every now and then, it is played on 2, or another number. Decks that are likely to use it include Thorn of Amethyst and Sphere of Resistance -based decks, which roughly translates to Eldrazi, and Workshops.