Nexus: Link to latest release of an artifact
I wouldn't use "LATEST" but if you want the latest release, you can ask with the "RELEASE" keyword:
http://somerepo.org/service/local/artifact/maven/redirect?r=central-proxy&g=groupId&a=artifactId&v=RELEASE
This will get you the latest given release, not just "LATEST" which will give you the last thing built (last thing uploaded for that group+artifact combo).