I saw a thread where someone was asking after mods that let engineers repair solar arrays; why not add such a feature to the game? If a solar array or extendable radiator (or other part) is broken, let an engineer repair the part at the expense of another part! When a specific part breaks on, for example, a station orbiting Kerbin, you'd be able to simply send up a cargo ship containing the new (working) part, and use up that part to replace the broken one, instead of having to replace the whole docked module containing the part.
