ATNS
ATNS have done work for ASECNA providing them with GPS approaches, In the case of ZS registered aircraft you have to have approval from the SACAA.
You cannot just go ahead and do GPS approaches without the aircraft properly equipped
The appropriate training done
Otherwise from what you say is that a pilot could just fly into a mode C enviroment without a transponder or TCAS enviroment or for that matter into RVSM airspace , without the appropriate equipment. I don't think so.!!!