The topic of this thread has earned my interest and I thought I could give some perspective that I have with my experiences.
I have worked for seven airlines of which I have experience interviewing with some of them including Southwest. I was on the interview team for several years in the last decade.
Pilot qualifications of who gets hired at airlines are very fluid with time. When the Legacy and Major airlines are in a large hiring mode, the qualifications of those hired are lower in that time frame. When the hiring slows down, the qualifications increase. Simple supply and demand issues. We did hire a few AMF pilots while I was on the team. At that time all the airlines were hiring and our min qualifications have always been higher than the others. For the time being, those times have changed.
There will always be exceptions, but as setting career goals and making choices towards those, if your goal is to work for a major airline, I would strongly consider trying to work for a regional that use RJs. When you are competing for a position and you have single pilot part 135 experience compared to someone else who has PIC part 121 experience, the edge will go to the part 121 experience. That part 121 experience does show in the interview process.
Now there can be the consideration of getting the 1000 hours PIC time at AMF and then get on to a Regional to get 121 experience as an FO while still qualifying for the good jobs out there. Although putting yourself in a more competitive position than not working for a 121 carrier, it does not make a large difference when you consider the pool of applicants today.
With all this said, as I earlier shared, there are exceptions. That exception is the "who you know" that most of us all are very well aware is important. Some candidates may personally know a Chief Pilot, or a respected line pilot or check airman, and that can help you get to the interview that you may not have been considered. I personally know Southwest HEAVILY relies on the pilot recommendation system that is in place. They post all the incoming interviewees for our pilots to see so they can easily write a recommend, or a not recommend (I will touch on this a bit later) online. A casual acquaintance will not get any preferential treatment. It must be an established, natural relationship so jumpseating around being a really nice guy won't get you anywhere. If any AMF pilots are getting good major jobs in this environment it is likely due to connections they had before they worked at AMF. I personally, as well as most of my co-workers, take the recommendation process seriously as it should.
Now I will address the "not recommends". We all know there are some out there that would not be good employees or co-workers. It is just life. Now it is difficult to be in such a dynamic environment without ruffling up a few feathers out there. Everybody including hiring departments get that. But how did you manage those differences? At Southwest if a candidate that interviewed well gets approval from the interview team for hire has a negative recommendation, they will call the person who gave the "not recommend" and get more information. If they deem it PURELY a personal difference then they MAY look past that. It has been done. But you really don't want to go that far and have it go down that road. The bottom line is try your best not to be unfair to anyone along your path. Take the high road with disagreement. Smooth it over before you leave. As the saying goes, "Don't burn any bridges" in this business. It is a smaller profession than one may think. If you screwed anyone over, or even if someone thinks you did, (who cares about the truth in this matter) and you want to work for an airline they are employed, you will be at a disadvantage. The real point is don't find yourself in that position. You don't have to. Leave ALL relationships with a positive future in mind. Try not to let your pride get in the way of a very rewarding career.