Mmmmhhhmmm. I missed that. Still, it would be a good idea to mention it in the list of special abilities.
True. But I figured I'd mention it. I can't think of any particularly large abuses that can be made of it.2. No, there really isn't. Those two abilities are mostly a mechanical choice because so many abilities depend on the Diadem. It only made sense that they didn't count against any soulmelds made and eventually become supernatural gaining the full effect as it is inherent of the PrC. Otherwise a simple dispel could take out more than half of its abilities. It also made sense from a flavor stand point as being a specialist of light.
Well, even if you don't take the Vows, by RAW, not only does a PC need the DM's explicit permission to take an Exalted Feat, but if they commit even a single Evil act, they lose benefits of their Exalted Feats-and therefore all the benefits of this class, since they no longer qualify for it. Granted there are ways to atone, but it isn't easy, and I personally as a player don't like things that take my abilities away for making a mistake. Still, it's your prerogative to design the class how you like. If I were to make a suggestion as to what to replace it with, I might put forward Soulsight from MoI.3. If you are talking about vows but there are plenty of no catch 22's such as nymph's kiss, sanctify x,..etc. I did it to fit the flavor of a good champion of light. Unfortunately there are no marshal specific feats and almost all of the Incarnum feats either require something else or don't make much sense. Also look in the special category of the requirments.
And yeah. Missed that.
Well, my thought was maybe it shouldn't, which is why I brought it up. But it's a fair amount of investment for another pool of Turning, so it's probably not as big a deal as I thought.4. I do actually, "This otherwise functions as the turn undead class feature," While it doesn't explain it all outright but it does mean you have just as much precedent in taking those feat as someone who actually does have turn undead. However it would make sense to exclude items as you aren't actually turning undead so you wouldn't use items that boost or contingent with it.
In any case, it is a very cool class.