For what it's worth, I don't think the actual changing of an extra setting is that big a burden: it's the figuring out that you need to change it, and how you should configure it, that is the problem. Especially since all major search engines still seem to return 9.4 (!) documentation as the first hit for a "pg_stat_statements" search. The common case (installing pg_stat_statements but not tweaking query id generation) should be simple.
the v2 patch I sent should address both your requirements.