Q: How do i Wipe Clean My OS X 10.9.4 for a fresh start when Yosemite arrives

Mavericks has nothing to do with Classic.  Please repost:

http://discussions.apple.com/docs/DOC-2463

Also I would not completely erase your system, I'd consider making a partition just for Yosemite to test your mission critical applications and slowly move stuff over until it is all compatible.

There is bound to be a lot that doesn't work.   Always backup your data before installing anything.