Doesn't really make sense that after a whole year surviving back there, Connor and Abby are banned from travel through the vortexes, but, I'm hoping it'll play out in good drama.
From another point of view, it makes perfect sense. The idea is "they've suffered enough." They've been through more than should be asked of any civilian, and they're the lucky ones, since other civilians (Nick, Steven, Sarah, and probably Danny, they assume) have died doing this work.
And there is real-world validity to that idea. In fiction, protagonists can go through horrible ordeals on a weekly basis, get injured several times a season, witness their friends and colleagues dying around them, and still be perfectly capable of functioning for five or seven years on end. In reality, people who go through ordeals like that are physically and emotionally traumatized and it would simply be cruel and dangerous to force them to continue. Real-life military personnel on hazardous duty get rotated back home before too long. Experienced or not, they aren't asked to keep risking their lives and their mental health indefinitely.
Really, after all they've endured, Abby and Connor should be allowed to retire on a government pension and get free therapy for as long as they need it. So while I'm sure the conceits of series television will lead them to get back into the game, the new policy of the ARC actually makes a great deal of sense by any realistic standard.
Becker seems to have stepped up a bit in his "leadership" role.
Well, he's the leader of the security personnel, same as last year, but Matt's the leader of the team and Becker's superior. So I'm not sure what you mean by this.