can you add a warn notice like this
http://dev.bukkit.org/media/images/83/969/2015-06-16_17.34.58.png

Wow. That would be really awesome.
It is a scientific mystery. Lots of players are able to write (to chat) but are unable to read it....

This way there is almost no chance to NOT see this message.

This would be 1.8 only and would require use of NMS/packets, as like @Kakifrucht said, there's no API for this.

I'm not going to add this into BanManager itself. If I get time today, I'll create a separate 'extras' plugin for this which listens to BM events.

I'll create a separate 'extras' plugin for this which listens to BM events.

Ok this is Verry nice

can you add too
Offline Warns

There is currently no API for titles.

If you want to get this behaviour already, you could use a plugin like TitleManager (which also supports an api) and add the command that displays the titles / actionbar to the warningActions list.

Looking forward to this feature :)

https://github.com/BanManagement/BanManager/blob/master/src/main/resources/config.yml#L104-L113

You'll need another plugin implementing some sort of title and actionbar command for this to be achievable, but it is now possible as of the latest developer build.