i created a patch for the userservice plugin.
With this patch, you can multicast a message to a list of users. This works without selecting them one by one in the broadcastmenu and without inviting them to a group first - you also don’t need them as contact in your rooster.
It is also possible to multicast the message to specified resources of the userlist only.
If, for example, testuser is running spark and miranda at the same time, you could send the message to spark only if you want.
This is nice for support and/or testing issues.
If you have some feedback, it would be nice.