I've added you to the Accumulo contributers list in JIRA and checked in a modified patch to contrib/trunk/bsp as a module of a new accumulo-contrib project.
I modified the input and output formats to have the following form because I didn't want to have so much duplicate code. This way, if the MR i/o code is changed, the BSP i/o formats will benefit from it directly.
public class AccumuloInputFormat extends org.apache.accumulo.core.client.mapreduce.AccumuloInputFormat implements org.apache.hama.bsp.InputFormat<Key,Value>
public class AccumuloOutputFormat extends org.apache.accumulo.core.client.mapreduce.AccumuloOutputFormat implements org.apache.hama.bsp.OutputFormat<Text,Mutation>
Let me know if you see any issues with this. It could probably use some more testing. I was able to get the unit tests working (even the part commented out in the patch) but I had to set fake input and output paths. It seems that BSP doesn't initialize the RecordReader and RecordWriter unless the configuration options "bsp.input.dir" and "bsp.output.dir" are set.