you said:
Redabot's custom-made telescoping arm breaks; Billy-Bob goes to Redateam's trailer, disconnects Redateam's practice robot's telescoping arm,

An arm is an assembly, not a part.
It would have to be diassembled to be brought in.
If it was not built during a fix-it window, any drilloing, cutting, etc would have to be redone from raw stock.