Not sure there are any good candidates for accelerating Energy for a Bronzong/Cheryl variant, but I suppose if you really wanted to play this card, you could use the Lost Zone engine and pair it with Zamazenta from Crown Zenith? Looking at tournament results from Japan on Pokemoncard.io's weekly tournament reports, you'll often see a Lost Box deck built around some seemingly random stage 2 ??, such as
Toxicroak ?? or
Lycanroc ?? . Hardly optimal, and for all I know it could very well be the same person each week, but I suppose if you really wanted to play Copperaja ??, you could use this method, and there's a decent single-prize basic attacker to justify leaning into Metal Energy. With everything else in the deck being a frail single prizer, having a bulky double prizer (as opposed to a frail double prizer) could have its benefits in certain matchups, and, since it evolves from a single prize basic, it prevents your opponent from being able to cheese prizes until it's nigh on impossible to take a OHKO. At least it has that advantage over running a thin Giratina VSTAR in a primarily single-prize Lost Box deck, though the latter is still superior in most respects, including having an extremely valuable VSTAR power and no weakness (plus hitting for 20 more damage).
That's the crazy thing about Lost Box. You have people pushing the envelope all the way down the competitivability spectrum, with the best players trying to find the perfect rogue deck or optimal formula, while more casual players try to find out what seemingly random stage 1 ??'s they can incorporate into a functioning build. It's the difference between "Miraidon doesn't live up to the hype, it barely wins a city championship a week" and "I wonder what would happen if I made a Miraidon deck with Luxray CRZ, Pawmot, Peonia, and Dream Ball" (
no joking, I've seen one of those lists in a weekly tournament report).
(Fun fact: all three Stage 1 ??'s mentioned in this article are illustrated in a non-3D style. I'll hopefully be adding these cards, not to mention Magnezone ??, to my collection this Christmas or earlier. The 3D-style ??'s are harder to choose between, but Spidops ??, Miraidon ??, Ting-Lu ??, Wo-Chien ??, Forretress ??, and Pikachu ?? are a few interesting ones I can think of off the top of my head. Actually, it might be choosing which ones I
like that I buy that proves to be harder.)