Falconson, you should try to contact Wizzair, it is even more experienced in Eastern Europe than Ryanair. I suppose LPP could fit their profile and to BCN they already fly. Theoretically they could use Poland- or Hungary- based planes with flight patterns like that:
Day 1: KTW (or WAW or BUD) - LPP - BCN - KTW
Day 2: KTW - BCN - LPP - KTW
Travelling from LED to WAW, BUD or KTW "Krakow West" isn't cheap either, so such kind of routes could also work well.