"I also figure to save costs that behemoths like MGM/Mirage and Harrahs could have a generic back up set that any of the properties in the same city could use if needed. Wouldn't be branded by casino"

That would not be allowed by gaming in NV and I doubt other states GCB would allow generic chips.

"but then again I haven't heard of a complete switchover being needed in LV or AC before either."

Back up chips have been put out quite a few times in all gaming juristrictions.

Back up sets are not required in NV. But, many casinos have them mostly for higher denoms.