I wanted to try the regular WW84’s head sculpt on the Golden Armor figure, but of course it’s incompatible (the sculpted hair prevents the head from sitting lower and it appears the neck socket is recessed a bit deep into the head and the GA figure’s neck is a bit on the shorter side). But I think with the head just sitting atop it still looks awesome.
Out of curiosity, I put on a spare Justice League head to try with the helmet. The JL head easily plugs in though the skin tone of the neck doesn’t match.