Synchronized Mining
All mines must be built at specific times. If you can't build the mine at the required time, you must resign (or allow your queen to be captured). Mines will be built on the 24th hour of the day specified, and can not be built sooner or later. Suggested mine schedule is as follows:
Mine 1: End of Day 2 (50)
Mine 2: End of Day 4 (100)
Mine 3: End of Day 7 (200)
Mine 4: End of Day 10 (300)
I don't know if this is actually a good schedule, so that might need adjustment, but I think this would be an interesting way to play. It would prevent stagnation of games because if someone starts to lag behind, they will quickly be forced out.