That was interesting read. I have few casual thoughts about it.
1. The actual delay will be slightly longer, considering time to verify block and not all node have direct connection to node on different planet.
2. On section 3.2.4, the paper mentioned miner on location 4 should choose mine on top of block that is less likely to be orphaned (rather than one with most accumulated work). What are basis to consider which block is less likely to be orphaned?
3. I see you write it under assumption light remains as communication method with lowest delay/latency. I certainly hope there'll be better communication option when human moved on from current (type 0) civilization.