Well the answer isn’t clean no matter which route you take. You have to remember that FOG doesn’t really care about user data or host OS. FOG (FOS Linux) is linux based so it really can’t step into the MS Windows world other than copying files to and from a MS Windows mounted disk. FOG (FOS) has no concept of user’s profile data.
With that said I can think of 2 routes. One involves FOG and the other is strictly a Windows activity.
For the MS Windows only solution use USMT (MS Windows User State Migration Tool). You run this from inside windows as an admin to backup and restore user profiles to a network file share. It works well for both same system user migration such as when the same computer is upgraded from Win 7 to Win10, as well as a different system migration between two computers. You can use USMT interactively of deploy the USMT Save State and USMT Load state functions via a FOG snapin or any other package deployment tool like PDQ Deploy.
Now for a FOG only solution. This task would be done with one of FOG postinit scripts. Where the script would mount the windows C: drive and rsync the c:/users directory to a remote NFS file share before the image is deployed to the target computer. Then after the image has been pushed use a FOG postinstall script to rsync the files back to the c:/users directory. This is not a very clean solution because ms windows won’t have the connection between the windows user account and their home directory.