Goat:
No, because FRA was full up and became slot-restricted some time ago, so new entrants cannot get established there. Same situation as at London Heathrow.
However, just down the road (in fact an awful long way down the road) is Hahn airport, euphemistically called Frankfurt Hahn and known to European travellers as "Where-the-hell-is-Hahn". It's an old USAF base about 60 miles from Frankfurt and Ryanair have it as an increasingly significant hub, and their usual cheap fares from there across Europe. There is a bus to Frankfurt. It was beautifully mocked in a recent British Airways TV ad showing a desolate terminal in the middle of nowhere with one rickety old Trabant (remember those?) on the taxi stand! But for low-cost from Frankfurt, that's what there is.