Let me prefix my question by saying that I absolutely adore M:TA. I love the idea to death, and the philosophical implications are wild and good for a lot of discussions.
However, I see problems with the idea of a paradigm within a mage character itself. I might be too influenced by my upbringing, but I'd argue that proof should always be able to change my mind.
Now, imagine being of any of the denominations/clans that M:TA provides. I use my magic by employing a fitting paradigm, be it "SCIENCE!" or "God" or any number of other ways.
Now, playing with other mages, every day I'm confronted with magic that does not work the way it works for me. I see a Verbena casting something fire-related just by chanting or gesturing, yet to do the same, I need to use a device? Something smells fishy here.
You could argue that I stick to my paradigm "'cause it works", and that's certainly a reason. But in the long-ish run, wouldn't I just be pretending to adhere to my paradigm, all the while I'm laughing my ass off internally because it all has become nonsense to me?
You could argue that this exact process is how a rising arete would express itself, but I could see most reality-grounded persons proceeding through this in a month.
I should end by stating that I have never really played M:TA, and therefor I am not familiar with the way this is handled in real games, or if it needs to be handled at all.