There is nothing to stop you from applying but I don't know how many would be hired outside of the flow, that's a great question but I don't know who would have the answer to that. Both Envoy and PSA are wholly owned by American so there may be some incentive for American to not do that leaving your realistic target as United or Delta outside of flow.
In any any event, my best advice to you would be to target airlines where you can sit in the captains chair in two years, ie - growing airlines. Airlines like Envoy, Endeavor, and Republic are so large that pilots are sitting right seat on the order of 7-10 years. It's counter-intuitive but some of these have or will in the future park airplanes for lack of pilots to fly them. Pilots refuse to work at these airlines because of the upgrade time. Why sit there for 7-10 years as an FO when PDT, PSA, Mesa, and TSA will have 1-2 year upgrades or less.
Again though, in a year from now who knows!!