The bottom line is this

Can Europe accept a nuclear Iran who promise to be fair supplier of energy to Europe?

I know that US will never accept nuelear Iran for strategic reason

Without nuclear, Iran issue would get more complicated. If Iran goes nuclear as it seems to show so far, it will change everything and become simplier. In that case, I doubt that Europe would go along with it and turn away from a nuclear Iran for just a few barrels of oil. US will step in. Europe has to choose whether to stand by and wish US fails in the end or join the fight to fair share of outcome. Russia and China, in this case, will diminish to less significance unless they join the fight to support Iran, which I highly doubt