could it also take on a meaning like 'potrzebuję czegoś trudnego' like talking about struggling in the study of a complicated subject as ' ciężko mi idzie' . ?? If so, could the English be 'I need something difficult'.
Not really, maaaaybe if the context made it completely clear what you mean, but I would still be surprised to hear something like that.
Well, it sounds natural. Maybe I need something heavy to make a counterweight.