[Spark_Ed]

You can reference specific move numbers from specific master games to compress. But you still need to compress how you store those master games. What you're describing for mid/late game might make more sense like this: you use a fixed version of stockfish to suggest moves (depth and version should be locked to static values so it reproduces the same engine move each time). If it's within the first 8 suggestions, you can flag that it's an engine move with 4 bits. Decompression time is significantly larger, but it maximizes the space for cpu trade-off.