I had a feeling it might be something like that. Maybe a greenhouse with an unglazed roof; get your light indirectly. But you've probably got the right idea doing it indoors, whatever it ends up taking to please the significant other.
That cabinet looks great. Why mess with success? If you did that I bet you could do something like this:
With your LED bars you could surely do an attractive hidden lighting job on a low-profile tank. And you might win some points if the terrarium serves a function with whatever space it takes up. Or is that just wishful thinking?