It may have run on the same CPU but NeXT hardware other than that isn't particularly Mac-like so there's no way on earth you're installing an old version of NextStep on an SE/30. At the very least you'd need the full source code, which nobody has, and spend a few months writing kernel drivers for the totally different hardware.Getting back on topic, how about experimenting with NextStep on the SE/30?
I know little about NextStep, but it did run originally on 68K processors, so it seems a lot realistic than OS X.