I've finally reversed the whole hardcoded logic again for the demo (because BinDiff wasn't able to handle small changes in giant functions). The positive part of that is that it made me point some small bugs I fixed in the full version.
At this point, the engine is only missing the MVE video player. I don't think I'm able to handle that myself despite TMM pushed the missing opcodes in ffmpeg. So, the engine is on hold undefinitely (at least until someone is willing to help me with that player).
I'm still tossing a coin to decide what I'll work on next.