BoxRec

These 3 fighters against next 1 Anthony Joshua. 2 Amir Mansour. 3 Gerald Washington

I would like to see Washington in with Mavlick Scott just to see if there are any truth in the rumours that gerald destroyed him in sparring, I would like to see Anthony Joshua in against Manuel Charr and I would like to see Amir Mansour in against Shannon Briggs

Joshua: Chisora, Takam, Ustinov, Teper

Mansour: Thompson, Rossy, Meehan, Briggs

Washington: Arreola, Boytsov, Charr, Wach

Actually, any of the twelve opponents I've mentioned would match up well with any of the three up-and-comers, and also match up well with Charles Martin and Joseph Parker.

I'd actually like to see Joshua vs Mansour

There's a LOT of interesting match-ups that could be made in the HW division if only the promoters, managers and boxers were willing to do it.

If I was doing the matchmaking with the fighter's best interest, not my own interests as a fan...
Joshua: someone in the #45 ballpark who is a minor step-up over previous competition, like Edmund Gerber, Denis Boytsov, or Eric Molina. I am fine with his team's choice to go after KJ for the power / deep waters test and Audley for the British money, though.
Mansour: an ex-contender with similar ranking who has little left to lose and little time left to screw around, like Ustinov. Some less exact matches may be Lucas Browne, Luis Ortiz, Malik Scott, Kali Meehan, Alexander Dimitrenko, or Eddie Chambers.
Washington: someone approximately #50 who can test him without being dangerous, like Eric Molina, Brian Minto, Franklin Lawrence, or Kevin Johnson. The better he's tested, the more safely you can take matchmaking risks with him in future fights.

Joshua will be wrapped in cotton wool.