Nihilego-GX, maybe?
Metagross-GX and Nihilego-GX, in same deck? My take on that? Who needs Necrozma-GX in that combo? When it comes to comparing confusion, poison and blocking potential retreaters outside of the event of Stand In, Guzma, etc., to discards after every attack, the confusion to both Actives is fixable by retreating anyway, but blocking foes from retreat on top is an option that could put Necrozma-GX into question in Metagross-GX decks.
^ Sadly, the deck still needs that Vulpix's beacon, as in this meta, you need a Brigette to use for getting three to four Beldum in play, and at least 2 metagrossess in hand in order to even get the deck's full potential out, and if you have to Beacon for the Metagrossess and/or Nihilego-GX, you're in trouble vs. the event of foe's Wally into Zoroark-GX T1(you have to go second to use beacon on your first turn), Mallow(foe's second turn after going first T1), DCE, and Espeon-EX with no energy in your discard vs. Gardy-GX and Zoroark-GX, to potentially-full-bench Riotous Beat to knock out one of the Beldums, or even win the battle by KO'ing a lone A. Vulpix if you can't Brigette, especially if you choose to go first, in which case you can't Beacon T1, and unless you have Brigette and/or drawn basics for placement on bench(to replace a KO'd vulpix in the event of a KO), the foe would have two chances to end it 5 prizes too soon by the whiteout(or knocking out the last pokemon in play, or the only pokemon in play), which is one too many today, even if it's a slow one. I believe Nihilego-GX saved Metagross-GX from being trumped by Zoroark-GX: Confusion and poison forces it to Stand In, which might not be present in its Gardy variant, Acerola/Guzma to bail out, or try to flip and hope for a good heads to ensure it doesn't get KO'd by 'Gross after the confusion 30 is applied...
^ Then again, Espeon-EX and its Shine is trouble to 'Gross if he materialized by Rare Candy, so maybe confusion and poison might be better suited elsewhere... I don't know where, but the answer to that elsewhere might be revealed later down the road, maybe not... Who knows what the future holds, and who knows what's a better partner for Nihilego-GX...
