Give the standard "user" group "ulx god ^" and "ulx ungod ^" (that allows them to god only themselves), disable server godmode.
Players would have to enable godmode on themselves using ulx god if/when they needed it, but would allow what you're asking, overall.
I'm pretty sure Admin weapons wouldn't hurt them still if they have god enabled, however, admins could ulx ungod <player> before shooting them.