Modulation diversity (MoDiv) is a simple and practical transmission enhancement technique that utilizes different modulation mappings to reduce packet loss rate and achieve higher link throughput. MoDiv is particularly meaningful and effective in hybrid-ARQ (HARQ) systems. We study the deployment and optimization of MoDiv for HARQ in a MIMOcoordinated multi-point (MIMO-CoMP) scenario under Rician fading channel to mitigate packet loss. We formulate the design optimization of MoDiv into a quadratic three-dimensional assignment problem (Q3AP), then solve it using a modified iterated local search (ILS) method. Numerical results demonstrate clear performance gain over simple retransmissions and over a heuristic design under fading channels.