All MS needs is to support Cisco AnyConnect and Cisco Jabber and they would be selling a bunch of phones.
The iPhones and Androids are like Photoshop, great software and total overkill if you just want to crop vacation pics. Really awesome that iOS/Android can do everything and then some, but most business users don't actually need any of that functionality. What business users need is to be able to stay in touch with and connect to the mothership.
Inexpensive smartphones that run Windows will only succeed in the enterprise market, and for that the enterprise apps need to be supported. Consumers will always buy those $700 devices for reasons unknown. Businesses will look at the price/performance and Windows phones shine in that, especially when Windows 10 finally comes to the phones.
Microsoft doesn't write the software. what you are saying is they need to get Cisco to support Windows phones. You are confused on your direction there.