If you know me, you know Dark Box w/ Mewtwo & Mew GX is a favorite Expanded ladder match choice. Though it's not quite BDIF, it certainly matches up pretty well against some big contenders on there: Dragonite and Shadow Rider specifically.
A prior version of this list can be found here: https://pokemoncard.io/deck/m3w-dark-w-techs-for-mew-vmax-etc-8781
To make space for AZ (a huge boost in consistency!) and Darkrai EX (free retreats!), I cut one of the Greninja & Zoroark GX's and one of the enhanced hammers. Even so, that hammer remains formidable. You only really need to hit one of them to get the jump that you need on Dragonite or ADP, plus a handful of other odd situations. And I haven't missed the second copy of Greninja & Zoroark GX like I thought I would. Huge thanks to some comments on Twitter to help refine this list! Comment below with any ideas to keep updating this one, keeping it relevant to the meta as long as possible.