Hello Intel Engineers!
I can confirm to you that there is a bug in the Cordova build for Windows 8 and WP 8.1
Two of my apps that failed to go beyond the splash screen on a WP8.1 device are now running perfectly when I used another IDE(MoSync)
The IDE generated a .xap file which is compatible with WP7/8/8.1
At this juncture, I think it's better for you to enable the legacy build for Windows 8/Phone 8.1 devices pending the time the bug is fixed.