During an IPC, is there any alternative to doing a precision approach? My friend's plane is IFR certified, but does not have either an ILS receiver or a GPS receiver, either one of which is required to fly a precision approach.  As he can't fly a precision approach in his plane, and such an approach is required to be flown during an instrument proficiency check (IPC), does that require him to find another plane in which to take the test?

Alternatively, can he take the test in his plane with a limitation being placed on the signoff to the effect that he is not qualified to fly precision approaches? Or does it not matter that a precision approach cannot be flown?
As far as I can see, there's no way to avoid flying a precision approach during an IPC. 61.57(d) says:


  The instrument proficiency check must consist of the areas of
  operation and instrument tasks required in the instrument rating
  practical test standards.


The instrument ACS requires a precision approach, as you said, and it's also in the checklist in AC 61-98C, Currency Requirements and Guidance for the Flight Review and Instrument Proficiency Check, and the FAA's accompanying instructor guidance. So I think it's fairly clear that the FAA requires it as part of an IPC.

As for limitations, the FAA's AC 61-65 Certification: Pilots and Flight and Ground Instructors doesn't mention any that are specific to an instrument rating. I've never heard of a 'non-precision only' instrument rating.

I can only suggest that your friend finds another aircraft. The 'good' news is that once he's current again, he can maintain currency indefinitely with only non-precision approaches and avoid another IPC.