I like the idea of the assimilated base not having a formula.
I also would like to see the dig times move around some. Each month - Week 1 they`re where they are now, Week 2 they move by 6 hours, Week 3 they move by 6 more hours, Week 4 they move by 6 more hours. See what I`m getting at? So each month they would make a full circuit. Then everybody would have a chance to dig at a decent time :)