MOSS Discussion Board with Moderator Comments

Question

I'm looking at adding moderator comments to the MOSS discussion board. The requirements are:

1. Moderator comments can be added to any message
2. Only a user with elevated permission e.g. a Site Owner should be able to add moderator comments
3. Moderator comments should be rendered differently to the related message
4. The modified list should be provisioned through a site definition (this is already taken care of but might be relevant to alternative approaches)

My current thoughts on this are:

1. Extend the list content type for Message to include a moderator comments section
2. Modify the schema.xml list definition file to render moderator comments, if they exist, in a different manner to the related message

Does anyone know of any pitfalls in the approach I've outlined, or know of a better approach altogether?