Well that is pretty great!
I already did try fading it out if it was parallel to the camera, the thing that doesnt work as expected was the transfer of Vertex Colors. so crossing planes most of the time doesnt have a similar color.
Here what I did instead was use a baked textured to color my cloud puff particles.
Instead of having them scattered with random rotations, i instead made the planes face the camera. manually rotating them when needed to hide them better.
BTW. the awesome plane animation was done by my brother 
just on topic…
the technique used on those nebula clouds are pretty much the same as I did with my other approaches :D. perfect if you just need to fly through them straight and just need a generic cloudy surroundings
but you can’t make custom shape clouds easily neither turnarounds
Yeah this is why i prefer modelling the clouds and scattering planes on to it, either billboard style or randomly rotated.
for further away clouds, i would probably just layer planes and shape them, but so far with my testing, modelling and scattered plane technique gives the best result, specially we have real lighting baked from the base shape, in my case I used Diffuse with a roughness of about 0.500 + Translucency. then bake it to a texture and use the texture to color my particle planes