Can you set up mapped directories with variables?  I am currently evaluating replacement sftp software packages for our university and we make extensive use of Active Directory users and groups for management of our current sftp solution.  One thing that make good use of with our current solution is the ability to define a single group of users and grant that group access to a specific share with unique folders.  For example if we have a class that needs web space on a development server then we would create a class AD group with all the students in there, create the folder and then give the group access to that folder.  Our current sftp solution allows us to define the sftp rights in such a way that when john.smith logs in and is in that class the server checks the class folder for his unique directory, if it's there it dumps him there, if not it creates it.  Much the same way that your home directions are defined (c:\home\%USERPROFILE%).