Last system bid Award shows two new hires got FLL right out of the gate. The rest got ACY.

What about DFW if you don’t mind?

dfw would take a while

My class earlier this year had everyone in their first choice straight of training (and we had people going to every base but Chicago) except maybe Detroit which took one extra month.
Don't sweat the NH bases too much. Things change so often especially once hiring picks up again that there's no reason to even worry about this.
Realistically speaking, unless you're in the pool now, the earliest you'll even be able to get out of training would be early-mid summer. No one knows what the vacancy will look like then, but whatever base you want shouldn't take more than a few months max.

If you're ok with commuting or live on/near the lEast coast, take a good look at the ACY seniority list. Less than a year after hiring, a guy in my class was in the top 20% there and was getting pretty much whatever schedule he wanted. There's a balance there, between commuting and getting your preferred line pretty much every month.

I added a Spirit profile, but the only job that comes up in their search function is the Base Chief Pilot for Orlando. And I'm going to go out on a limb and say that's not me. Any idea when First Officer applications will be open again, or am I just not smart enough to operate the Spirit Careers website?

Everyone expects it to be posted sometime after the new year.

Or shortly after the merger.

We have to staff this airline until then.

No everyone doesn't. When was the last time the Board had a meeting? If it was on the Horizon as you say Wall Street would know and the Stock would reflect the business change. Fact is we have Pilots running around make stories up. F9 used a common part number and it's yellow so it's a merger. You're claim of just after the new year? What year??? Ask a Board member if you want to know not a line Pilot.