eJ will only hire FOs through flexicrew regardless of previous experience. There was a very brief campaign for direct entry SFOs to go to the new LIS base but I don't know what came of that.
Honestly speaking on flex terms eJ is a decent enough hobby during the winter and a decent enough job in the summer but it's a long cry from a career especially if you want to stay in the UK as permanent contracts are few and far between - most of them having gone to the continental bases over the last year with nothing planned in the UK until after the summer.
Basing on flexicrew is completely haphazard, you will go where you're told to go (at your own cost) and stay there until you are moved again with a month's notice. There is a 6 month limit for continental bases but that doesn't mean you get sent back to the UK afterwards... I have been very lucky only getting based in places I want to be but I know others who have been uprooted fairly often.
Job security is also what you make of it. In practise if all goes well then all goes well but the legal papers say you can be dismissed for just about anything - failing a sim, going sick, being late, or the company just not needing you anymore. If the wrong people don't like you an excuse will be found. If you're joining experienced and rated it's not so bad but the cadets are walking on thin ice and I know a few who have been sent home with a £35k loan and 100h on type.
Command depends on your factored hours and the amount of other qualified people in the queue, with a permanent contract of course. I've heard it's something between 2 and 4 years now.
All the 737s are gone now, last 737 drivers are in line training on the bus. There may be a few DEC positions for LIS but only for people with time on type.
Just live everything else it's what you make of it. Some love it, some hate it and others just get on with it.