In regards to the 'main book only' protest, I suggest the archetype builder puts in 'if X then A, if Y then B, if Z then C, if not, then Q' series. If you're using something from a new / 'fringe' book or supplement, note where it comes from, then say, 'if this is not allowed, use G or H' where G comes from one main supplement (like Run Faster) or H comes from another one (like, say, Run and Gun), then add another statement of 'if this is not allowed, then use P', where P is from the main 5E rulebook.