Not sure if this is already planned or not but a couple of items to add improvements to mining. Could call it Advanced Mining as a researchable item. This should provide things like:
1. Allocate priority mining areas per digger. In that you can have diggers focus on separate areas of the same mine. You may want a digger to prepare a ramp to lower levels with other diggers focus on extracting ore.
a. This could be by setting the main area to be extracted from a mine then divide that area between diggers. When they complete their own task they can then default back to main area of the mine to be extracted.
2. Allow trucks to be filled by more than one digger at once. So that if 2 or more diggers are there, they can all fill a truck if they have same resource and truck is within range. Seems weird that diggers can sit there doing nothing when 1 digger is slowly filling a truck.