How about a button on the HUD (with a keyboard shortcut as well) that opens a strategic screen with small depictions of all planets that you have a base on, all with strategic icons. Then there would need to be a way to toggle scrolling on each planet on the fly. Perhaps holding shift / middle mouse button while highlighting a particular planet hides the cursor and instead allows mouse movement to pan over the planet. Like this, but less MS-Paint-y. Also, if there is to be a more traditional minimap option, I think it would look nice as just a 3D, fully zoomed-out view of the planet, perhaps with a zoom slider on it. This would allow you to see at least a larger chunk of the planet than you might be looking at with your current level of zoom, and the center point could move with your camera.
Or just have each of the planets in your proposed layout spin fairly fast so you could quickly see the full 360 degree strategic view on all of them at a glance.
You can have both. A button that toggles rotation with a slider to change the rotation speed. Plus manual scrolling as I described.
Oh no, I meant a viewport of a planet that rotates around the planet. Providing you with 360 degrees of strategic information without displaying the planet rapidly spinning or being at night when it's actually day.
Ah, I see. Well that's basically what I mean. It would operate the same way moving your camera in normal play would. It's your camera moving around the planet. I just explained it backwards.