I like this! The (apparent) simplicity and strongly constrained perspective are appealing. You should be careful to preserve them from interference. For instance: I think the blue edges are now overdetailed compared to the 1st versions. Many small items are inconsistent. The bg and meteor 'free style' strongly contradict the style premise.
Generally and without giving it too much thought, I found I wanted it to lean towards those classic ptoing pixels:
The emphasis on 45° lines, strong volume rendering despite near abstract perspective and shading, importance of highlights on edges: these do or could apply to your piece, at least potentially. Of course you might choose a different approach, this is just what jumped to my mind
Whichever, consistency will be key.
Perspective: your 'impossible' postulate being that both vertical and horizontal surfaces are rendered undistorted as if seen frontally, there can be no foreshortening, squares must remain squares.
Consequently, the platform at center top should have 45° corners like the main floor and everything else; the spaceship reactor casing should be as 'wide' as it is 'tall', etc.
Light: good thing to have flipped the floor tiles edge highlights from back to front, as these now look like bevels lit from above and help perceiving the tiles as horizontal (compared to vertical before). I would like to see lower contrast on the dark lines to help them read as the opposite side bevels.
Generally I see this with a top-down light source for whatever is on the platforms, and another (blue?) source from below for the platform edges. This would impact the spaceship side too.
Background: this is going to be hard! How to keep it from being a distraction, consistent yet readably different? No clear idea but it might be worth trying washing out any details, either in bright light or darkness:
Have fun!
