No advice here, just feel the need to chime in:
I’m seriously surprised there’s people contemplating leaving BA for J2 (never mind actually doing it!). I’m Dutch, and flew if Europe from 99-05, ended up flying LoCo in the USA. Nobody leaves DAL/UAL/AAL to come to Spirit. Back then everyone in Europe wanted to get on with the flag carrier of their country. Can’t believe things have changed so much that people would leave a multi year career at BA and start over. I know commuting is a hit on QOL, I do it myself. Have working conditions deteriorated that much at BA?