Hey Clark,
I wouldn't recommend trying to hammer the "Systems" idea from AutoCAD MEP into the hole available in Revit MEP, it's just not going to work. We have already discussed much of this topic already in previous threads, so I won't re-hash everything.
Before I go into any detail, I have the following questions:
* What specific tasks are you trying to accomplish with the "pre-defined" systems?
* What is the "pain" that is associated with the definition if systems in a new project?
Required reading:
Blog Post on System Discussions
http://inside-the-system.typepad.com/my_weblog/2007/11/insight-into-sy.html
Another blog post on System Discussions
http://inside-the-system.typepad.com/my_weblog/2007/12/more-interestin.html
Let me know the answers to the above questions, and if the linked posts provide any clarity.
Cheers,
Kyle B
Revit MEP Product Manager
http://inside-the-system.typepad.com/
Kyle Bernhardt
Director
Building Design Strategy
Autodesk, Inc.