Isn’t this simply impossible from a political point of view?
The answer is probably yes, but 25 years is a long time and thinking could change 180 degrees in that much time.  Even so, if you drop the literal creation of a county, the endstate has many ideas that are possible and it has found widespread support as a direction.

What was the motivation that drove the consolidation of the Forest Preserve?
A more contiguous Forest Preserve would be one that isn’t right up next to hamlet land and wouldn’t include small isolated parcels that provide no ecological benefit.  The motivation is primarily ecological health that arises from larger contiguous tracts of Forest Preserve land versus scattered disconnected parcels, but reduction of pinch points with communities is also a benefit.

Why is privatization a necessary counterpart to centralization?
The theme of this endstate was low-cost government and government that performed more like the private sector. Privatization is one way to do that and get out from under government employee healthcare and pension liabilities.  The jobs don’t go away, instead they move to private contractors.