Wouldn't work dogplatter.
If your "Invisible body" was the cause of solar eclipses, it would mean that a solar eclipse could occur when the moon is anywhere in the sky.
But that's not the case.
Solar eclipses only occur when the moon is directlly infront of the sun. In the nights leading up to a solar eclipse, you can actually watch the moon move closer to the sun, and if you have the right filters, you can see the moon just before it blocks the sun out. I'm sure you could modify your hypothesis to include this, but it seems like you are making it uneccesarally complex.
At the very least, I think we should be able to agree that the moon is the cause of a solar eclipse. This doesn't seem to violate any major principle in FE.
Now as to the causes of the moons phases:
Go outside on a day when both the moon and the sun are in the sky, you can see that the illuminated section of the moon is always pointing towards the sun. Not some of the time, always.
This is the strongest evidence that the sun is illuminating the moon, it makes your invisible body completelly uneccesary. Of course, for the moon to be illuminated in the fashion that is iss observed, it would have to be a sphere. I have already posted my evidence for that, and you never did really give an adequate response. . .