Your concern for the buyer is admirable. However, for a buyer to be offered possession 10-20 after the closing could present a multitude of issues. Buyers actually take ownership at closing, not a designated period of time after it. It's unlikely that most buyers would agree to this arrangement.
Buyers should understand the terms of their agreement and what it means for them. The fact that deals "fall apart" is reality and can happen for any number of reasons.
Unwaveing Commitment to Service
This is why professionals should insist on working with local loan originators. When trouble occurs the Utah based originator knows agent in FL or Ohio will not be appearing at their door. If your buyer or seller would like to risk momentary homelessness, they can choose to ignore the advise of those who have been doing this for more than a few months. How we start our clients in the very beginning has a lot to do with how the final hand will be played. Protect your clients, your broker and yourself... possession after closing ONLY!
This is not leadal advise but there are liability issues on both sides. Occupancy at closing is much cleaner.
It's a stand-off.
I want to avoid this whenever possible.