Banning Poketurn is just silly, it makes SP pretty much unusable, not to mention Gyarados would be rampant if your suggested bans were made.
The answer is not to ban a certain card which completely eradicates a decktype. As I said before limiting the card to 1 per deck seems logical to me..
Limiting Sabelye to 1 means the chance of a T1 collector into giratina mesprit and impersonate cyrus initiative isn't going to happen that often and there would be less t1 donks.
Limiting Crobat to 1 also decreases the chances of a T1 donk - most SPs and other stage 2 decks only use 1-2 anyways.
And lastly limiting Uxie to 1 is a MUST. The amount of times I've seen someone come back from nothing to a winning position by setting up for 4-5 cards is ridiculous , heck I've even done it myself. The card is ridiculous and limiting it to 1 is VERY fair. 2 max. Banning this card outright would slow many decks down too much.
Why not limit BTS: stage 2 decks and gyarados would be less viable, leaving sp to sweep
poketurn, cyrus, egain? sp would be unusable, leaving vilegar, gyarados etc to sweep
pretty much what I'm trying to say is that limiting these 3 cards would make the playing field even after the implementation of B/W rules.. all decks would continue working as normal, and sabledonk/lock doesn't destroy everything in its path. IF you think sabledonk/lock sucks, try getting powerlocked, judged or let loosed, as well as losing up to 2 cards from your now 4 card hand. this leaves you wiht 3-5 cards in your hand + whatever basics you started with, good luck trying to win. add chatot stuffing up your draws and sableye or garchomp romping through your basics... you're in for a rough ride.
......either that or just don't implement the rules yet