Sounds like a good idea.
But I dont belive Blabberize is that advanced, in that you only have the option to turn all of a particulars users to blabber or not.
You can't actually set it for a particular post or board.
You could I suppose, add a bool column in the posts table and then work off that so a few adjustments will need to be made to the mod at hand for your required result.
As an idea? maybe add one line to the dointerest cron job that will reset these variables.