This doesn't apply to the gen3, but the gen4 Jimny I believe has a variable displacement oil pump, which means a gauge won't actually tell you a whole lot as the pump will change flow rate depending on RPM and oil pressure - if the clearances in the bearings increase it will still try to maintain the "correct" oil pressure.
I'd be interested in knowing how you came to this conclusion, there is no mention of it in the factory service manual, and the pump appears to be a conventional "trochoid" type similar to what I've seen on several other Suzuki engines, the only thing unusual about it seems to be the location, in the timing chain cover, which, incidentally is also where it is on the later gen 3 Jimny with the M-series engines.
According to the manual, the oil pressure is checked in pretty much the same manner as I've seen it on every other Suzuki I've looked at, connect a gauge to the pressure switch port, and measure the pressure at 4000 rpm with the engine warm, 40.6~72.5 psi.
I'll agree there's not a lot of information to be gleaned from fitting an oil pressure gauge, yes, the flow rate will vary with engine rpm, (it's a positive displacement pump) and the delivery pressure is regulated by a bypass valve that diverts flow back to the oil pan. All "very normal" and "very conventional"
