@import-once is implemented in recent versions of dotless and less.js but is not recognized by Web Workbench. This would be extremely useful. Thanks!
Heck yes, please. We're working on an internal framework powered by LESS and this would be amazing.
The latest nightly supports @import-once!
Unfortunately, there's an outstanding LESS compiler bug that causes duplicates still, if you reference an import in a nested import :(
https://github.com/cloudhead/less.js/issues/884
