Sounds like a good idea. YAB wouldn't be that useful here, though, as it's not present by default. Maybe even just a (local) web page would do, though, as I don't think it would have to much computing. I guess it would be in the 'launch' folder so it would appear automatically at startup.
As well as pointing to WebPositive, it should explain HaikuDepot, and tell how to get the User Guide from there. What else? A short list of useful apps, maybe. And of course a link to the forum!