I'm not sure if this answer is going to hit the exact point you were looking for, but Conversion Disorder can run an extremely wide gamut - but is typically contained to a single part of the body (arm, leg, eyes, etc). As for the severity of the manifestation, consider this: One of the most fascinating examples of a conversion disorder is called hysterical pregnancy, whereby a woman will go through ALL of the symptoms of pregnancy - including a growing belly and lactating breasts. So yes, the symptoms can mimic a TIA, although remember that the T stands for "transient," meaning that the issue would resolve relatively quickly.
Oh, and I forgot to address the first part of your question - Conversion Disorder rarely comes on slowly, It is a pretty immediate reaction to some traumatic stressor, although a hysterical pregnancy does require 9 months to fully come into fruition. I think this answers all of the questions you have presented. If you are satisfied with the response, please hit "Accept." That is the only way I can receive credit for my answer. Thanks-