> I don't really get your problem as saturation functions (and thus endpoint scaling if I understood EPS correctly) are independent on PVT properties, right?

Yeah, you're right.  End-point scaling and hysteresis affect saturation functions only (i.e., relative permeability and capillary pressure) so the problem is less severe than I originally imagined.  That does however mean that we can't pass the region index into the functions that compute saturation-dependent quantities.  In general, calculators need the actual cell index, whether the end-point values are given by cell or by depth.