Well that is why I suggested Elaine. As far as I know she is avoiding the Council, or might even be unknown to them? Marcone as a signatory of the Accords may be able to offer her some protection, at a cost. She knows Harry, and his magic, another big bonus to Marcone. Marcone became the protector of Chicago when Harry was shot, and is probably allied with the paranet which could have been how he would learn of her.
It's just theory, and thought it would be a fun topic since the forums seem a little quiet.
Elaine has gone to shady people for protection in the past (Summer, possibly Cowl if she's Kumori). A situation like hers may be the only way to convince a wizard to sign on for Team Baron Marcone. Someone like Elaine, or Hanna Ascher (who may or may not have had a wizard-level talent before picking up Lassie), for example. Personally, I think you'd be hard-pressed to find a wizard who's willing to do work like that, when most of the ones we've seen A) don't want to work for anyone but themselves, or B) don't
have to work for anyone unless they're pursuing a specific goal that requires allies. Even then, I'd imagine it'd be temporary.
Still, it's possible that Marcone has found one. However, I think it'd be
far more likely that Marcone would try to find a wizard
child, one who was particularly vulnerable (say, like Harry and Elaine were—orphans, confused, alone, destitute) to raise. Doing so would provide the benefit of a wizard ally in the future, and would fit Marcone's history of going out of his way to protect kids.