Can't you put down some helix anchors outboard of the hull, attach float lines to them, and then pull the boat away from the wall when you secure it?
That would not be allowed. I am in a state owned harbor and the only thing you can do is tie your boat to the existing dock cleats. On big surge events some boats set an anchor to try to keep off the dock. I have not tried this as I do not think it is worth the effort. The scope would be less than 1:1 and the harbor bottom is mostly silt- not much holding power. Additionally, if there is a boat next to me (we are in double wide slips) the line to the anchor could interfere with their mooring or the entering and exiting dock.