using ImageMagick via systemcalls.
I've clients where imageMagick is used for image handling (better than gd) which are called form php with the system call. with safemode all system calls are disabled. This could be tuned by the execdir flag but i dont know if this would be very compatible with all the different linuxes.
The open_basedir flag operates on its own, so using this security feature does not reley on safemode. In my view the open_basedir should always be set on a shared server. If the safemode would be operated seperatly in isp config on could allow system calls (safemode off) but still limit the scope of php to the open basdir settings. See also the numerous posts on cms and other software pacjages where the safemode has to be set off. In most of them even with safe mode off there could be extra security with the beasedir setting in effect.
Now ispconfig toggles both at the same time, so you get safemode with openbasedir or no safemode with no openbasedir.
hope thats enough to make my case?