I really doubt this will ever be used in any functional way. Seems like it is just for aesthetic purposes. They are way too difficult to tell apart from across the table, especially when ships are covering up most of the surface area. Would be a neat concept though.
The idea is interesting, but starting with all the planets face-down would make for a less attractive table layout.
You can't both be right - the background colours can't be both difficult to distinguish and essential for aesthetics. I don't imagine you've ever actually paid much attention before I sure hadn't. But I tested it yesterday, and I challenge you both to do the same.
We played last night, and I made a point of trying to notice planet surfaces. First of all it was easy to distinguish the various faces - even from across the table - with minimal effort and attention. Second, some players had there planets mixed some face up and some face down. This also required a minimal amount (but more than no amount) of effort and attention to notice. Conclusion? The surface are easy to discern if you try to, yet the backs are easy not to notice if you aren't trying.
As for the backs becoming marked, isn't this the same way moons were handled? I don't see how this would be worse than moons. Regardless, the planets don't have to start face down in order to utilise the colour distinctions. They can start face up, and offer a one time effect that you activate by turning face down. Or you could start with extra abilities and lose them as you lose home colonies on corresponding planet types. Or simply leave them face up, and make the rule that win with a one foreign of each geo-type. The later makes for a longer game but also more interesting ally dynamics and ship stacking tactics.
There is lots could be done with these planet faces - both official and house.
Have to agree there. Tops are different for visual appeal; bottoms are the same (and not full color) to minimize production cost. End of story.
Sounds like speculation to me. Personally I'm inclined to think the faces are different for a (mechanical) reason, otherwise why not make the faces all the same to minimise production cost? Like adam points out, you don't notice these unless at a glance. Time will tell.