Welcome to FT,
Wax!
Could the OP route the following:
AA 856 STT-BOS 3:10-6:25
AA 1491 BOS-STL 8:20-10:35 (next day)
May not be ideal, but could be better than overnighting at MIA, and earn more miles in the process
AA really needs to retime their limited STL-MIA service to help it better connect with the banks they currently have. I would like to see the route go from 2x 757 to 3x 738 but am not counting on it anytime soon.