The topic is not to remind us why we don't like crunch. Its not just DnD...it is relevant to any game with a system. There always exists the potential to break down a mechanic or process to exploit the boundaries of the original idea/character/etc. Thematically, i understand the idea of the AoP. But, it is not alone. There are a bunch of wonky themed prestige classed, some of which are can be exploited to manipulate a portion of the power curve, mainly rewriting its own in comparison. It is the same thing as a power combo in CCG's. The AoP is a perfectly viable idea...I am coming from a point of role playing. The crunch that goes behind it, just needs to be thought out better. AoP is exactly what i was designed to be, a Prestige Class for a celestial themed splat book, designed as a resource, just like the Book of Vile Darkness. A lot of the presentation involved justifying Crunch with Story. The Story needs to come first, and be the origin of you perspective, in order to avoid labels, and other terms that other people reading may find offensive. Oath of Poverty, Oath of Peace...sounds like good story stuff. I know the 3.5 crunch. My suggestions are not for 3.5, it was for pathfinder conversion. Play up on the theme of peace. A trained martial artist who doesn't fight, and uses inner peace to promote peace and non violence...to me sounds super awesome Monk story goodness. Monks still often are part of the clergy or church structure, or it could make clerics more monk like as part of the goodies of the not yet created Apostle of Peace Pathfinder Prestige Class.
And the Oaths are fine as well...that is a good hook. Make it a life choice, rather than a career choice. Those are easy enough to bring over or up to pathfinder...In a medium or high magic world, as pointed out, may make that more the drawback when your party is armed to the teeth with magic at level 10. Still, I just don't run 3.5. I will play it if i am comfortable with the other players not being crunched to the max. I will run pathfinder cause its smoother, and seems to be efficient when paired with people that know the system well. AoP could fit into any game, just needs to repainted and brought in line with the boundaries of Pathfinder.