Re: Good distance ?
Good question Lars. I think it depends on your combative situation. I can speak on MMA. For the example you bring up with MMA, you might leave front foot light if you are trying to keep distance and want to have the front foot mobile. However if you are closing distance, clinching, or doing take downs, maybe not so much and you might be a little more even weighted or front weighted even. I think you can adopt such a strategy when you are conducting sports because you have so much knowledge about the situation and can pick a stance, posture, balance that allows you to exploit the situation you are trying to shape.
In combatives however, there is alot you don't know, so I don't think you always have that luxury. Based on your observations, on the various styles you mention, I'd say all of them are highly stylized training methods that favor certain things either based on training methodolgy or sporting aspects, for example in Muay Thai.
So again, I think in reality, we don't always have the luxury of isolating out rules or have knowledge enough to allow for such exploitations. Therefore, I think you will see a much more even or balanced approach to things when study in this manner, or when studying combative principles.
Anyway, hadn't really thought about this too much so these are simply thoughts off the top of my head. Again, A great question to ponder!