It is a very specific issue; it's the only sane case in which twelve massive entities are supposed to be inside each others' bounding boxes, a case in which the other side of a planet is never visible from one side, a case in which there is automatic gravity... A lot of changes and fixes can and must be made to planets specifically.Planet performance isn't a specific issue. Its an issue with performance on big structures. And the plans are to gradually improve them through alpha and beta.
Well we've been trying to figure that out since we first started drawing maps on flat sheets of paper.I wasn't able to find a good way to map a square onto a sphere so I'm kind of neutral on the matter. (You can do it, but there are mathematical problems that make things strange.)