Many years ago, I designed a set of tongs capable of lifting a billet of steel weighing 60,000 pounds.
The trick to these tongs was a mechanism allowing no one to be around when they were clamping and un-clamping on billets of steel.
The mechanism looked like a ball point pen on the inside and allowed the crane operator to lower the tongs over the billet, stop and then lift to engage the clamping force as it lifted.
When the lift was done, he set the billet down and continued to lower the tongs until the mechanism caught the groove which kept the tongs open and allowed the tongs to leave the billet.
The pictures show the tongs, a close up of the mechanism, and the load test at 120,000 pounds.
We have actually used this principle in a more recent design. The tong experience allowed us to solve a problem for a client that was really out of the box.
Let us look at your problem. Maybe some of my old project solutions will work on present day issues!