Workflow and revisions (diff module compatibility)

I would like to modify the workflow history tab so that it allows you to do a diff comparison between two revisions of a node. An example of where this might be useful is where a user submits content for review, the moderator sends it back for review, the user resubmits with changes, and the moderator wishes to compare the new content against previously reviewed content.

The diff module allows the moderator to compare different revisions of a node, but does not allow the moderator to see the corresponding state changes of the node, so in the example above the moderator does not know which revisions have previously been reviewed.

Has anybody attempted to implements similar functionality? Would this be a desirable feature to include in future versions of the workflow module?

I have hacked together a solution which relies on recording the vid of the node each time the workflow history is written to. I have also hacked the diff module so that it retrieves information from the workflow_node_history table.

I can upload the code that I have written if this will be helpful.