You need not to install everything if you know at least a bit what you are doing. Just do upgradepkg without the install-new parameter. Required packages are described in tagfile in every packages section (a, ap, d, e, f, k ...) and only these need to be installed by upgradepkg --install-new.
Just FYI slapt-get dist-upgrade command does this automaticaly for you.
I use this practice for a long time and didn't have any serious problems so far. I like to keep the most stripped down installation with a must packages only.