ERS at plant/vendor level

I am at a customer where they are trying to do ERS ant plant/vendor basis- what I mean is- Say vendor ABC supplies material to 5 diferent plants and due to GR processing/ and other issues at couple of plants they want to set up ERS but not at other plants.

has anyone come across this and if so how have you worked it out? And is it reliable?

Second question- when setting up a vendor for ERS- what flags need to be checked besides- GR based Inv.verific and Auto eval GR setmt del?

Thanks

Raj