Rarely do political actions such as discussed occur in a vacuum. Remember the emancipation proclamation was issued in Jan 1863 as part of Lincoln's re-election push. Take into consideration that 2 states were excluded from the proclamation, Missouri and Maryland non-secession states. That raised the ire of Radicals and stirred the emancipation pot in Missouri particularly. So is it hard to imagine radicals taking the issue in hand and working to develop an "army"/ PEMM to free the slaves. We do know that a number of PEMM units were aggressive in liberating "property" and thus the pressure on Gamble to reel them in.