So, umm... I kinda borrowed the Lunar Ponies idea for a story I was writing, I hope that's okay. I gave you credit, and I'm trying to make it not clash with your fanon, but of course it already does cus they survived... Unless Viva had A LOT of foals that were all somehow pure lunar pony.
It's a very interesting design. Though personally, I want to know if those little spike-ity thing-a-ma-who-zits on the back of her hooves have any sort of function, or if they're just there to look cool and differentiate the Lunar Ponies from regular pony-folk and terrestrial donkeys/mules.
I will repeat what I have written down for the first time that Viva had shown up, in Lunar Shadow 10.
"Acording to the "Ask Viva Tumblr": Lunar Ponies "see" darkness; they see well in complete darkness and have poor eyesight during the day. The leg horns are a biological failsafe anti-vacuum defense; basically a 1-minute breathing limit to return to a non-vacuum area, although Lunar Pegasi can breathe completely in vacuum. Lunar Unicorns can use Lunar Radiation as a magic source. The Lunars can also, because of the ears, survive in extreme environments; they are practially invulnurable to extreme temperatures. Males have more elaborate heel spikes; which are considered desirable for mating purposes."