I'm going to say something crazy, that I would rather gamble on Cousins. Personally to me, I think a team with legit big men are historically a matchup problem for any LeBron led team in the past.
LeBron pre-Miami lost to the Celtics 2 times since assembling the last Big 3
so in the playoffs that LeBron has lost in the past, a serviceable big man or star big are usually involved
2008 - lost - KG/Perk
2009 - lost - Dwight Howard
2010 - lost - KG/Sheed/Perk
2011 - lost - ehh I guess you can say Dirk/Tyson
2012 - win vs OKC (no star big man that can score)
2013 - win vs Spurs (sure but I still felt like the Spurs choked)
2014 - lost - Duncan/Diaw (also the emergence of Kawhi)
2015 - lost - Green/Bogut
2016 - win - (GSW choked, and I also blame Green in getting himself suspending, turning the series around)
But yes, I do believe that with a good big man lineup, we are legit contenders
Horford/Boogie lineup looks very dangerous in my opinion