This is not possible.
The channel protocol of a single process assumes the full MPB is available for itself; if 2 MPI processes are launched in the same core they will interfere. Also, using other libraries that access the MPB is not possible, for the same reason.
The MPD process manager tends to oversubscribe the cores when launching multiple MPI jobs. In order to launch multiple MPI jobs with the MPD, one has to rely in host files.