As an agent, if I had any inkling that a buyer was trying to add an extra 60-70 days to an escrow, I would totally smoke out the buyer.
A notice to perform to remove contingencies followed by a notice to perform to close escrow followed by a re-list on the MLS as active subject to cancellation of current escrow.
In other words, if the listing agent were to give you that much latitude, I would find his conduct questionable.
That being said, the way you want to do it is to claim it as a lending issue and to offer some concession that appeals to them.
Let the deposit go hard, offer additional monies in a way that makes sense.