Declare built-in client detection as deprected in favor of Browscap and Mobile Detect

How to achieve this? I notice SYSTEM:USER_BROWSER has version number but, SYSTEM:USER_OS/SYSTEM:USER_OS_SIMPLIFIED does not. Both will return 'Android'. So the operator (>, =>) cannot be used for Theme Switching Rules ?

I would like Android 3.0.x - 4.0.x : Theme A
Android >4.1 : Theme B
Android <3 : Theme C

Other alternative?

Thanks