Laugh all you want mate, I didnt know they were to place it so far away from earth, however both are well clear of any significant atmospheric interference, and thus its feasible to put James Web at 600km, in fact, why so far away? So far means you have less of a window to use the earth as a sun shield.
They originally planned to bring it back incidentally, however obviously no longer. James web is 6.5 m, while hubble diameter is 2.8m, but longer, it wouldn't be impossible to modify the shuttle payload bay in orbit to accommodate hubble, also you could probably take James web + orbital boost rocket in the shuttle at the same time. Plenty of fairly good ideas, but obviously they wont be done, it could be done though theoretically.