it's a fun idea. sure, there is some element of danger, but the risks are no greater than hand catching mavic.
I would use rubber bands around the body/battery of mavic to secure a short piece of rope that has a hook on the end.
Dji actually has an official video of matrice delivering a bag of goodies this way. They use like a 6 foot rope with a hook furthest from the drone. This is likely a good idea.
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I second the above poster that you should not use the rear legs. Rather, for max stability and weight lifting capacity, the hook should be near the mavics center of gravity.