I'm not so sure about manoeuvrability vs firepower, especially in case of Protector, and considering that tau ships speed is still average at best, even with added AAF speed, but then, as I've said before, I have no real experience to judge.
About stealth system, well, I personally would prefer something maybe not so powerful, but more reliable (and, I suppose, it's kind of typical for tau themselves). Also, I consider stealth as one of the main themes of tau army, so I would really like to see stealth elements (both in WH40k and in BFG) more often.