If your lawyers are "going to try and wrap up every single detail without considering any of the downside risk," you should get better lawyers. In particular, I find transactional lawyers have a much better "deal sense" than litigators moonlighting at it. Once you've found a lawyer you can trust, you're more likely to trust his or her judgment more on what the legal risks really are.
If it's the other side's lawyers who are overlawyering the agreement, why not politely suggest to your counterpart that they, not their lawyers, should be driving the deal?
>Why not suggest that your counterparty, not their lawyers, should drive the deal?
Because here we're talking about sales, in which asking your counterparty to do things they don't already intend to do injects friction into the process, thus reducing your chance of closing the sale.
If it's the other side's lawyers who are overlawyering the agreement, why not politely suggest to your counterpart that they, not their lawyers, should be driving the deal?