Since your first entry into Schengen is at FRA why don't you get a visa from the German embassy?

AFAIR your visa should be issued either by the country of first entry or by the one where you intend to spend the most time, so either should be able to do it.

Also, the French should be able to accept a ticket to/from your first point of entry (i.e. FRA)... after all it's not that uncommon for people to travel by train or car, so I don't think they could insist on your ticket being to/from an airport in France as opposed to elsewhere in Schengen.