Cargolux is not commutable anymore on the new contract, unless from the neighbouring countries. Only 9 days off per 28 days when you start instead of 11. And only 35 days of leave instead of 42. Its only after a few years that you have the the full off days and leave days. Salary is also 3 steps lower than it used to be. Upgrade is more than 10 years, so not before he retires, if that's what he's looking for.
Low cost in Europe?
EasyJet or Ryanair? He might be able to upgrade after a short while. Stable 5/4/5/3 or 5/4 roster and a good network to commute. Not sure, but I think that EasyJet offers a bond for experienced FO's instead of having to pay for the type rating.
WizzAir offers Rapid Command for experienced FO's. Type rating, upgrade training and line training all in the left seat from day 1. No need to pay for the rating, only a bond. 5/4 (actually 1 rest and 3 off) or 14/7 rosters are available. The salary might not be as high as EasyJet or Ryanair, except at Wizz Air UK, based in LTN. And the commuting options are limited in Western Europe. Lots of commuting options in Central and Eastern Europe though.