I see both Harris and for sure Watson as better prospects than Laurant even with his experience, could be completely off here. Both of those guys have the build to be contributors early really depends on how they develop as the season rolls on. Just my $0.02.
I think Kalib Boone will be the back up 5 right now. Pretty thin right now but a capable rim protector. But not as many teams play in the low post anymore. Kansas would pose problems. But it's nice having athletic 5's that can move because they tend to guard the ball screen (a far more used action) better.