ikiwiki's .setup file can specify wrappergroup, and ikiwiki will set the group of the wrappers accordingly. Having had people encounter difficulty before when trying to do the same thing with users (for instance, making all wrappers 6755 ikiwiki:ikiwiki), I think it would help to have "wrapperuser". This could only actually take effect if building the wrappers as root (not really the best plan), but ikiwiki could at least warn if wrapperuser does not match the user the wrapper will end up with.