It would be a good idea to standardize a “docking bar” so that robots can suspend themselves from an already elevated robot.
An initial suggestion would be to make the docking bar a pipe similar to the TOWER pipes: 1.5" steel pipe with something at the ends to prevent robots from sliding off. Like a towel rack.
Compliant robots would have this docking bar attached to to the side opposite to their lifting (elevating) mechanism. Compliant robots better have a steel frame to avoid being pulled apart.
Some sort of visual target would be nice too.