Let's see what all three would do to the meta-game:
DRE: Suddenly the slower decks comeback. I could certainly see GG becoming mainstream again, and Flygon would get even more popular. Overall, I see this as a healthy change. The fast decks still could compete, but you don't need a T1 donk attack anymore to do well. Gives us even more of a variety.
Cessation Crystal: This card...is going to hurt a lot of decks. OK, after I get set-up, I simply attach Cess. Crystal onto my Active Pokemon, and you can't use your Uxies, Mesprits, Azelfs, Crobat Gs, and Claydols. Dialga G has proven Body-locking isn't cool either. Both of these combined is just sick. With nearly all decks relying on Draw-power these days, Cessation is NOT good addition to the format. We need more in the Supporter drawing department before we even dare look at this card again.
Windstorm: With Windstorm, SP decks are a thing of the past. Energy Gain and Unown G are both vital to those decks, and without them, SP decks are too slow and are crushed by Machamp. Gengar gets hurt a little bit, but then he gains a huge power boost in the end, no being able to snipe Claydols and Uxies without a care. BTS will be a thing of the past, too, and decks will start looking like Pre-Platinum decks again. The lack of Unown G, however, could make some cards more viable again, especially Special Conditions decks and decks with damage counters. Still, I see too much Gechamp domination with this, as Champ beats down your Basics and Gengar picks off your draw-power.
Here's a suggestion created by me:
-GET A BETTER SUPPORTER DRAW SYSTEM!!! Really, what do we have for draw this format? Felicity, Buck, Mars, POV, Volkner's and Mom's Kindness. How about refreshment/disruption? TGW, Looker's, Rowan, and Cynthia's. Considering some of those cards are bad, and some only work in certain decks, we need to get more in the way of draw support. With more draw support, decks wouldn't need Claydol and Uxie so bad, thus knocking Gengar down a notch. With more draw, I could see SPs and speed decks dropping a Uxie or so, though they will still keep 1 or 2 on hand. With a better draw system, some of the other cards listed could come back without as much harm, and Power-locking wouldn't be as much of an issue. Overall, this would be a welcome change for the format, and we wouldn't be screwed over when we DO lose Uxie and Claydol. Budget decks would also start to exist again, as now they wouldn't need two or three $20 cards.
A better draw system would be the best for the format, IMO, but if I had to pick one of the three listed, I'd go with DRE. GG still wouldn't become a dominant force, people.