It appears that the only function of librmi is to export the VM function JVM_LatestUserDefinedLoader. It seems really silly to have a whole native library to perform such a trivial operation. JVM_LatestUserDefinedLoader is also used in java.io.ObjectInputStream.
It would make more sense to put an entry point in sun.misc.VM, and have rmi, ois invoke it. This would completely eliminate the need for librmi.