Strangely enough, the idea is in play and being negotiated, principally with the Israelis who have not dismissed the idea out of hand.
It is true that the original mandate precluded the deployment of soldiers from any UNSCPM, but that was forty years ago, during the cold war and changing the terms of the mandate is quite straightforward. There is no doubt plenty of horse trading to be done, but I suspect that underlying all of this are two immutable facts:
1) Russia will not allow the fall of the Assad Government and even the popular tide inside Syria has turned against the rebels.
2) The main concern now is stopping spillover to the rest of the region and greater global blowback.
Beyond this of course even if an official UN mandate is not forthcoming, Syria as a Sovereign State can simply invite Russia to provide this border duty.
A few weeks ago an Al-Qaeda affiliated brigade did briefly overrun a Golan position, causing the retreat and subsequent withdrawal of the Austrian forces. The Syrian Army quickly retook the positions, which were technically in breach of the Golan Armistice, but Israel made no complaint. This clearly indicates to me where they now see the greatest threat to their security as coming from and that the Russian solution is the only practical option available.
