are there any updates for your MOD?
In my experience it's not really needed to create an extra class for this job. There is only a need for two new functions - one for checking and blocking and one for reporting.
After analysing what the existing Akismet libraries are doing I've noticed that is not a big thing to get Akismet integrated into phBB3. It can been realized using a lot of existing phpBB3 core code.