Really nice idea, I like it. Nice art, too. And the idea to make Morning Sun and Eclipse cancel each other is wonderful.
However, I totally agree with what has been said before: upgraded version should cost 3, not 4, or I would definitely not upgrade the card. Of course, keeping the symmetry with Eclipse is important flavor-wise, but you end up with an useless upgrade.
There's a solution: make both Morning Sun and Eclipse cost 3. This way, the symmetry is preserved, and the buff to eclipse is somehow offset by the fact that it now has a counter.