In my personal opinion and limited experience, I think there are so many thousands of ways a team can be built and played, and there is never a guarantee of being truly unpredictable, as that is more about your own play-style and experience.
There is most certainly some extremely competitive teams and players, but I am sure if you ask most would happily keep your secret to themselfs and let you daze and amaze the next batch without spoiling the surprise.
If it is a extreme secret/game changer, best case is to try and keep it as close to your vest as you can, get your mons yourself or only one from each breeder, aswell as mix it up, battle with other strategies, and then just whip it out at worlds and be like, hey, Look at me now!
Also, Want to confirm, if I have a pokemon dreamworld account, with both a black and a white cartridge on it, I can access the dreamworld twice in a day, once on each right?