I wasn’t planning on answering my own question, but it seems that I found out exactly what I was looking for only it has recently being added to sass and will be available on sass 3.4. I believe there’s a prerelease to tried but I havent tried it yet.
Basically what I was looking has been answered to me on github:
https://github.com/sass/sass/issues/286#issuecomment-49112243
So on 3.4 you can do:
.level1 {
.level2 {
.level3 {
@at-root #{selector-append(".blue", &)} {
color: blue;
}
color: red;
}
}
}
which is exactly what I was looking for.
There’s a bunch of addition related to the parent selector (&), you can learn more from it at https://github.com/sass/sass/issues/1117
Bear in mind though, that at the time of writing this answer, all of this is rather new.
Also see: https://github.com/sass/sass/blob/master/doc-src/SASS_CHANGELOG.md
And: http://www.phase2technology.com/blog/everything-you-need-to-know-about-sass-3-4/