Bump + Message
Sounds fun. I've seen this done on TF2 before (If someone on the losing team leaves, a message is displayed center screen "RAGE QUIT!", and an announcers' voice says "RAGE QUIT!". I love it.), and it would make me oh so much more happy to see this in BL too, but with your own serverside message. :D
Also, to all those people who are complaining whither or not the leaving player is actually raging, this would be just a fun mod. If you leave seconds after dying, it could cheer up the server seeing that there's not only one "frustrated" player. This mod, I like the idea. Those who think that they would gain bad rep for it can give reasons, but this can also assume great comedic timing.
/support