I thought I should write for such a case cause seemed interesting to me, and its already implemented at eXpand.
How you do it?
1. Create a new eXpanded Application Solution
2. run both the win and the web client so both model will be created and saved at the database byt the modeldifference module.
3. Clone your web model to a role model
4.Assign the roles you want to change (you could assign all roles of the system if you want so the model will applied everywhere)
5. Make your changes (eg. apply a different navigation menu)
6. And since that model is going to be loaded every time a user log on to the system so you only have to log on again to your application in order the model to be refreshed and reloaded