This reminds me of a personal alignment question I have. Wide neutrality vs. narrow neutrality.

It's easy to picture alignment as a 3x3 grid, where the population sorts evenly with 1/3 lawful, 1/3 neutral, and 1/3 chaotic. When actually discussing it, though, the actual arguments tend to tilt either narrow neutral (those who lean towards an alignment count as that alignment are that alignment, neutrality requires either focused balance or utter lack of aligned actions), or wide neutral (an aligned character must be an exemplar of their alignment, since anything else is neutral).

I still think that wedding a poorly-defined moral system to the rules is foolish, but you might be better served by better adjusting your neutrality expectations than trying to say that only certain people, who happen to have a class that runs off a certain stat, can ignore certain inconveniences while everyone is stuck with them.

Plus, again, alignment-based outsiders. A solar certainly has the stats to ignore alignment. For a being of pure Good to become a blackguard seems like it would smash the intent of your rules, even though it's a perfect expression of the mechanics. Alignment-based outsiders tend to be high-level foes, with correspondingly high stats to match.