You can annotate parameters and then use those annotations in libraries that rely on reflection or in IDEA inspections. There are no principal problems with that. You just need to write those libraries and inspections.
Additionally you can change scope from IDE to Project with one of the buttons in right toolbar. If you do, .idea/IntelliLang.xml file will be created in your project, so that you can share it with others, e.g. by putting it in repository
And one more clarification for earlier mentioned user defined @Language annotation.
In fact you can use annotation with custom name, placed in custom package - you just need to set it in Settings > Editor > Language Injections > Advanced > Language annotation class, where org.intellij.lang.annotations.Language happens to be default value.