If Ryanair want to join the dots, then this leaves very few airports in Central and Eastern Europe that they don't already serve from LPL- Brno, Balaton and Bratislava, plus a few extra cities in Poland- I doubt there is enough Czech or Hungarian workers in the northwest to provide the VFF traffic that LPL attracts on its Poland routes. I think Bratislava could work, due to its proximity to Vienna, but Wizzair have already indicated that they will serve BTS from next year. This leaves only Poland, which must be close to saturated with 3 carriers, serving Warsaw, Krakow, Katowice, Gdansk, Wroclaw and Poznan.
I never seem to understand FR logic (how the hell can they make Tampere, Alghero and Ancona work?!), but surely it would make more sense to serve Frankfurt, Brussels, Eindhoven etc first before launching more routes to eastern europe which don't attract business travellers so much as lower yeilding returning-home Polish workers.