dog,
I disagree with a few of your comments.
1. To maintain gold or platinum status you have to do a minimum number of AA flights but the challenges do not have this requirement.
2. Just talked AAdvantage customer service again and no prerequisites for gold or platinum challenge. You can do one or the other your choice (occasionally I have heard of folks being able to sign up for both at the same time) no need to be gold to sign up for plat challenge. Of course, considering AAdvantage cust service and the different stories you sometimes get whenever you call you could have been told something different but when I did it was told no requirements and was just told that again 10 minutes ago.

Otherwise, welcome to ft mike.

jerry