Wow, great work, this reminds me of a lot of demoscene stuff where, when faced with space limitations, programmers aggressively used procedural generation combined with prerendering and caching.
The most iconic example I can think of is .kkrieger, the 96kb first person shooter that has (relatively) amazing graphics: https://en.wikipedia.org/wiki/.kkrieger
I have kept in contact with both of them a tiny bit (through twitter, blogging, etc); both Bran and Miguel are very talented people and I consider them some of the top in the field of voxel engines -- Ken Silverman as well.
The most iconic example I can think of is .kkrieger, the 96kb first person shooter that has (relatively) amazing graphics: https://en.wikipedia.org/wiki/.kkrieger
Video here: https://www.youtube.com/watch?v=2NBG-sKFaB0
There might be valuable lessons to be had in that domain that might save you some time.