Variables that can be changed include pack opening speed, the ability to open multiple packs all at once, the number of packs that can be held, and how fast cards are picked up/placed
Similarly, if a cost includes causing you to gain life (like the alternative cost of an opponent's Invigorate does), that cost can't be paid
We perceive removing Phlage, Titan of Fire's Fury as a meaningful hit to a few of the strongest decks in the format
Most people dont want it or like it
Consisting of Ancestral Recall, Black Lotus, the Moxes, Timetwister and Time Walk, the Power Nine are some of the most powerful cards in all of MTG so powerful, in fact, that they were removed from the Revised printing after the release of Unlimited Edition