If I'm allowed to pick hypothetically Matthysse would be good. I'm trying to think of some fast fighters... If he could get him, Keith Thurman is a good combination of speed and power that could help him out a lot.
I once read he was fighting some good sparring partners from the underground boxing world. their names are leonardo, raphael, donatelo and michael angelo. could be some cab drivers but we dont know, i havent seen their resume in boxrec.
i actually heard he brought this guy into his camp called master splinter to help with his mental conditioning.
I think its easy to read too much into sparring partners. Its nice to have guys who can emulate a particular style. But fighters have to be very careful about bringing dangerous guys into camp. The last thing Bradley needs is to be going through pier six brawls every day in camp. I remember reading that Margarito went to war every day with Buddy McGirt Jr. before the Clottey fight, and it showed when he turned up flat for the bout. If Bradley spars with Lucas or Thurman, he's just going to get brain damage. Carlos Quintana might be good. Maybe Sechew Powell, if he's still fighting.