@Spidy.
You say it wont be BDIF. But dont qualify what you mean by BDIF. Just what do you call the deck that has a 60% advantage over the field?
No one would mind if this 60+% deck took time and skill to play. The complaint is because it doesn't. It is flippy-mon personified.
Its mere existence as a possibility requires that players have to counter it or join it. So assume that everyone tries to build a counter deck as joining it leaves you with an expected 50% finish on the day. Just how effective is that counter deck, because it needs to be a serious threat and not just a 50-60% deck vs sableye. How do you build an 75+% counter to sableye without losing to just about every other deck? The first step is to realise that whatever this counter deck might look like it is a deck where your opening seven cards are all that matters. The second step is to know that you have to be able to cope with the opponent going first. That only trainer lock, power lock, or just massive HP from your basics has any real chance of working.
Trainer lock = 4x Spiritomb (approx 50% chance of opening with this)
Power Lock = 3x SP and a Spray (tall order from your opening hand!)
Massive HP = 4x Reshiram, + 4 x Zekrom + more BIG basics. (but it is still unlikely that you will start with three big basics)
or a blend of the above.
And the trouble is that the opening hand statistics are against you unless the only deck you want to beat is Sableye.
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Uxie Donk failed as a tournament deck because it could not win until after the opponent had a turn. The opponent had Call , Gastly, and half the time access to a power spray as ways of stopping the uxie-donk. All of which feature in tournament decks.