Couldn't agree more. I would say the criteria for the prize would involve power, emissions, specific consumption/efficiency, mass and use of recycled materials, not in that order. Thats why diesels would do very well.
Im pretty sure an r32 rb25 and r32 rb20 have very similar inlet manifolds, my guess would be that your mate has a complete r32 rb25de motor including the head.
Never heard of the external oil feed failing, anless it was done incorrectly, should be more reliable than the plumbing for an oil cooler, and you dont hear of them failing. An rb30 turbo head is the same as an rb30 head
As i said, if its a djetro, then it will have two o2 sensor inputs, as its made for an rb26, not rb25. And tuned correctly, you will geet better fuel economy with the o2 turned off