I have to disagree on several points.
Occitan was already in a better position against French at the time from a cultural point of view. Occitan literature was far more brilliant than the one available in Langue d'Oïl (although the Languedocien from Toulouse was probably more prevalent than Provençal in the Gallic area). But...Dante was born twenty years after the Albigeois crusade that crushed any possibily for an autonomous "Occitany" : Bordeaux is too Plantagenet to become the cradle of a unified Occitan language (and Gascon is quite peculiar, anyway) and Provence is more Imperial than French at the time. The political conditions that Dante had in Italy simply didn't exist at the time.
For the record, it is Francis I who imposed French (or the dialect from Tours, to be more accurate) as the official language of France. Not Louis XIV. The poor man was too busy with setting Europe aflame to cope with Occitans (well, except the Hugenots).
Last but not least, there was no unified Occitan until the Félibrige, a cultural movement in the 1860-1870 which unified Occitan grammar and vocabulary, and if you're true when you're implying that people from Southern France were speaking occitan dialects until the second half of the 19th century, I'm afraid that, speaking in their own dialect, a man from Bordeaux and a man from Marseille would have understood each other, but with attention from both of them.