(Necro?)Bump.
I’d like the very same thing - do you mid sharing your script? Just so I get the idea – I’m not that good at sed stuff… Or is this possible now native hugo?
Well… as I bumped I feel I should share my personal solution.
For sections i just move the content of the section folder - excluding index.html - to root and replace every occourence of ‘/content/’ with ‘/’ find $folder -type f -print0 | xargs -0 sed -i 's/\/categories\//\//g'
I didn’t change post folder, as I kind of like it now ^^