I have built 16/16 imperial levels, however the death Star behind the emperor is not complete (missing a small portion on the top). More disconcerting is that the imperial "mission" tells me I must build another imperial level in order to see what I must build next. It costs 100 bux to skip. Is this a bug, or is it simply wanting something from the "coming soon"future updates? Has anyone else experienced this or found a fix besides paying to skip (which may result in it happening again)?
Tiny Death Star is still receiving updates occasionally, which add more levels - including Imperial levels. It's certainly possible that such a new Imperial level might enable you to complete this mission in the future.
It is also very much possible for the emperor to ask for a currently impossible level to be built. This could be considered an oversight or a bug - neither of these is confirmed and we can't really look into the developers' minds on this. Support for Tiny Death Star is also abysmal.
If you wish to proceed with the missions, you will either have to wait for an update that adds Imperial levels, or skip the (costly) mission.