Droopystop,
Make calls on the Air/Ground frequency - even blind calls if necessary. Separate yourself from anyone who has recently called up in the same position as you are shortly going to be in.
In VMC, there is no need for any additional protection because your primary means of separation is lookout. In IMC, no one will be flying unless they are IFR. So prohibit IFR flight in an ATZ in IMC without making the correct radio calls, and the problem is solved.
After all, the US has plenty of instrument approaches outside controlled airspace, and aircraft don't fly into each other too regularly.
Incidentally, this could apply to any (approved) form of instrument approach, it doesn't have to be a GPS approach.
FFF
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