It took a few days for me to genuinely think of an answer to this question. I came up with three streets.Where would a woonerf be *needed*, though? Not a hypothetical, but which actual Minneapolis street?
One could make the argument that a woonerf could be built on Chicago Avenue between S 6th ST and S 4th ST outside the stadium. This section actually makes more sense now that I think about it more and more. Secondly, if the city ever wanted to open S 2nd ST between Hennepin Avenue and Marquette Avenue or even S 2nd Avenue a woonerf would fit that area nicely (not that I know if this is even on their radar). And lastly perhaps across the river along Main Street between NE 1st Avenue and SE 6th Avenue.
And really, these three candidates are all sort of halfway there. So... ¯\_(ツ)_/¯