Japan is good an AONE4 ex South Africa is still cheaper.

If you want to maximise BIS miles then this is something very different than maximising miles actually flown in F, as most routes don't have (proper) F anymore. Or maximising the lounge experience which is much better on OW than Star Alliance.

Usually people don't want to maximise BIS miles on a AONEx but want to maximise the F experience.

So BIS from NRT could be something like this:

NRT-DEL-HKG-BOM-HKG-LHR-MCT-AMM-LHR-LAX-SJU-ORD-SEA-DFW-BGI-JFK-NRT (50548 miles)

The North American routes change all the time so LAX-SJU or flights to/from BGI might not be there all the time. But there is always something.

Or plan B:

NRT-CGK-HKG-DEL-ORD-SJU-SEA-ORD-RNO-MIA-JFK-SYD-AKL-BNE-KTA-SYD-NRT also over 50k miles.

But they are not really great if you want to enjoy F.