That's not how things go. Many have asked already, and some have started providing patches, but nobody finished the work. You're welcome to try and go the last few miles if you feel brave enough; or just restructure your Maven project to follow Maven best practices.
I think if we could, we'd remove the dependency altogether by splitting javax.validation support out into a third-party lib; but unfortunately javax.validation has crept into other parts of the codebase (request factory, editors, themselves now deeply interleaved with widgets). Splitting is possible, but demand some efforts, and it's easier to just use separate classpaths when invoking GWT to avoid conflicts with server-side dependencies. I'm still hopeful that we'll one day replace the build system with something easier to maintain and allowing more modularity, but for now I'm waiting for GWT 3 work to start (or at least have some visibility about what it could look like).