re -

Remember, both GPS failure AND vacuum failure together is a very rare
event. Do teach your student to do a VOR and ILS approach partial
panel and without GPS. Don't waste your time teaching him how to do a
LOC or VOR with FAF defined by cross-radial that way - it's just not
worth it,

I trained by student to do just that, with a non flip flop VAV, and he
got it on his checkride, and he passed.

Andy