Can TC improve the IQ of original lens?

It is maybe a crazy question, because as we generally know, any additional optical element can only make the image quality worse. However, theoretically it could be possible, that the additional group of lenses, (what a teleconverter consists of) may compensate for the optical deficiencies of the original lens. If you use TC, have you noticed something like that? I have a SMC Pentax A 70-210/4, which is fine at the f-ratio over 7.1, but fully open it is pretty weak (exhibits rather a significant loss of contrast). It is a cheap lens, so I do not expect too much out of it, but, what if a good TC can improve its quality? Thanks in advance for your thoughts.