How to become a seasoned security SW architect

One way is to learn from Landy Wang:

See:

http://www.microsoft.com/about/technicalrecognition/landy-wang.aspx

“When I approach a new project, I quickly envision the ultimate goal regardless of the constraints of the existing architecture, anticipate the potential pitfalls, come up with solutions ensure that the changes will fit seamlessly with the current system and then confidently proceed full speed ahead to completion,” Wang says. “I don’t like to compromise the fundamental tenets of the design process or any of the implementation of that design because doing so can potentially impact the entire ecosystem that is supported by Windows.”