I don't think it's very hard to EMP harden anything that has a physical size less than a few hundred meters. The power grid is in danger because there is a huge potential created over very long distances. I think to be protected from EMP just requires isolation from large DC voltages, which can be done with an isolating transformer and some varistors? But something which is not miles long and isn't connected to the grid won't really be touched by an EMP anyway.