NOTE: I know very well this isn't a plug-in, but I have found it very useful.
I wrote this a very very long time ago, modified over time to reflect changes to output messaging.
I finally added this Module in one of my public repos, here: https://github.com/edhaack/teamcity-service-messages
Honestly, it's nothing Earth-shattering, but it really is useful (IMHO) and saved me time hunting for the correct verbiage and value modification to conform to the output requirements.
Really would love to hear your feedback