That's a good idea, and one I had not thought about previously except when I needed to dive into my own custom management pack. I'm not sure what you have to gain by stripping something out of a default SCOM management pack, unless your company was not using SCOM.
I am always trying to put extra code on top of the defaults, so now I will remember to look inside some of the default packs to see how they are getting the job done. One thing I have been struggling with recently is setting up a way to customize the discovery of a service (i.e. Sybase) in a similar fashion to how MSSQL is discovered. This would make the custom groups and rules I create much easier to administer.
Anyway, thanks for the tip, and I look forward to reading more.