Could it be possible for you to add backward/forward support? Mainly for the mod.
Currently, you have to be on the same exact version of the server. This makes it virtually impossible to update the plugin because if you do, the entire playerbase has to reinstall/update the mod on their client, which can be confusing for some people.
It would be amazing if a player using a mod version older than the plugin version could still use voice chat. Same with vice-versa, a player using a version newer than the plugin version can still use voice chat.

What you say is not true at all. Please read the wiki (Compatibility tab)