I doubt it, Nic's back up plan was he knew exactly how Murphy would react. She told Harry how she felt earlier and Andruiel heard it all. So he bluffed her into breaking a Holy Sword, if she had accepted his surrender of noose and coin, he'd be in the same boat as Cassius.
I think "Murphy loses it, and Nic breaks the Sword" was Nic's
primary plan. Indeed, with Michael (apparently/supposedly) out of operation, Harry going to Murph was the odds-on favorite, and Murph being manipulated that way might have been one of Nic's main objectives (even the topmost one) in that
ENTIRE project of his!
I think Nic's backup -- in the unlikely event she
didn't lose it -- was that he knows the Coin-Summoning ritual (the one Lasciel's Shadow offered to teach Harry), so he could call it back at his leisure.