Hi, @Balint Oberrauch Its been a while since I played in the Profile game, but I would look to do a mandatory profile and store it on the C: in your image, especially if you won't be updating it very often. That will eliminate even having to read it over the network on logon.
I'm sure that there are plenty of articles out there on how to set one up, but it usually entails just logging into a Windows machine and configuring the settings that you want for the user (keeping in mind that you COULD set some of those up with GPO, but that would also increase the logon time). Then logout of that account and copy the c:\users\%username% folder to a new location and change the ntuser.dat to ntuser.man. You can also set the folder to .man (considered a super mandatory profile) but, I don't think you'll need that