WRT to "Muscular Neutrality", this is one of those themes that can/might benefit from a few rounds of "why-ing". It's something I occasionally do to themes I dislike to see if I can come up with an underlying premise that gives me a better hook to explore.
As an example:
Why is muscular neutrality needed?
= There are no "natural"/"automatic" forces that maintain the Balance
=? Why does the Balance need to be maintained?
== Because if it is not, the world will "drift" too far in one direction in planar space, and be subsumed into another plane, destroying the world.
==... And those who are tied/influenced from a vector opposing the drift will be destroyed first.
==... And oppositional resources will vanish too (i.e. If you're drifting away from Plane of Earth, those magical gems and metals will vanish)
...
So now you have "activist" factions, trying to steer the world one way or another, and some factions just going "oh h*** no, we want to keep our stuff", and all without the (IMO) distasteful flip-flopper, who looks at their True Neutral alignment as prescriptive instead of descriptive, and alternates aligned deeds.
Also, keep in mind Dragonlance, where in the history of the setting, Good actually WON - and then bad things happened. Muscular Neutrality is preventative measures, if you ascribe to this philosophy/interpretation.
Edit: To be clear, I don't think any of these are the only interpretations or "why?" answers. In fact, the differing answers to these kinds of issues is what make a setting Yours, not Mine, and not Theirs either.