While I agree that using ESAs is a much better approach than forced consolidation of districts or supervisory unions, I suspect that you are dramatically overestimating the likely savings. In our district, I would not expect any administrative savings, because we have already moved administrative services to the supervisory union and it is large enough that there would be few additional economies of scale. If we combined with a neighboring sub and eliminated a superintendent we would probably need to add 2 deputies. Same for business manager and special education director.
We could save on outplacement of special education students and on curriculum director and professional development costs, but I would be shocked if the total net savings was 3% of our budget.
Studies from other states have limited value. What we need before moving ahead is a detailed examination of a few possible specific mergers to determine what positions might be eliminated, what new ones would be necessary, what other savings are likely and the cost of leveling up teacher salaries.