I'd rather accrue seniority at the place I'm going to have to bail for rather than take a bonus to live in base for a year or two, then end up as a permanent Jr DEC.

My advice would be to grab the bigger FO bonus offered by the wholly owned, ride their seniority list up, and if Compass actually does lose the flying, get your LAX base with Envoy (should that be the case, you'll have the seniority to hold it).

Worst case the Compass birds go to someone other than the WO you end up at, you'll still upgrade as soon as you've got 1000 SIC, and you'll be in the pipeline for your career airline. That being said you can still apply to the other majors, and the one you've got flow or a preferential interview with.