The problem is that we already have a layout based on how users actually search. That is to say the same structure as the roms. This is also important for other database reasons.
Manufacturer -> Model -> Platform of Emulator -> Emualator -> Version
eg
Nintendo -> NES -> Android -> Nesoid -> v2.5.0
We can change this layout. If we do we will break all the existing Google page links and that would be bad. If you think about it, this is also the most common way that people search. They search for the system they want to emulate first, then the device they are going to run it on and then the version of emulator for that platform. Not the other way round.