Not really to sure. there hasn't been any trainers focusing on HW's apart from Steward with Wlad.
AS mentioned before Joshua has natural advantages but he will need a trainer who can teach him from ground up. Someone hwo can remould him into a boxer puncher. There is no way he should go to Booth, mckraken as their students, Froch, Groves all like to war and it seems Joshua cannot take a shot to well. He needs someone like Hunter, Richardson who is a great tactician who will devise game plans that stick to his strengths. I can imagine Joshua turning into a wlad type fighter who can KO you but wont put himself at risk due to him having a poor chin. I hope some day the young Erislandy Savon turns pro in the USA. He looked like a LW but with HW size.