Move to a model where each can provide their own device. What happens to people who may need a top-end model for work, but can't afford one? Especially when senior management, who can afford the latest toys, are provided with phones that they don't use or understand.
This is the jealousy conundrum of allowing free use of personal consumer devices at work. And your mobile policy had better address it, starting with needs analysis.
This is particularly useful when it comes to tablets, where nobody really needs one yet but it might make a useful addition to the fleet of toys. A good way to smoke this out is to ask whether someone is willing to give up their laptop in exchange for a tablet. Most of them will suddenly reconsider how important it would be to them.
I've found a matrix mapping tasks to needs to devices is incredibly helpful. You can use this to define the priorities for each device. Adding whether the task touches sensitive data, if relevant, and you have the beginnings of a simple risk assessment table too.