Just my two cents, but I think autoinstall(8), install.site(5), and rc.firsttime(8) would work a lot better for mass auto installs of OpenBSD for customized (or 'desktop') installs.
If a person isn't doing mass installs then I don't see why it would be needed to install a tool to install a desktop to save time when its easy as: $ doas pkg_add mate-desktop chromium $ which mate-session >>.xsession
