If you have the chance, how would you fix the mess the show made? (pretending this is Tracy's last season too)
Honestly, at this point, I'm not sure. A few weeks ago there was a theory floating around that Sean was behind the lack of communication somehow. And that's something they could do, so let's go with it.
In 10x04, Hailey made it seem like the lack of communication to that point was expected. And to be honest, it would be. Networks can take a while to set up, and until they are, what little connectivity is had (SAT phones and such) is prioritized for the work. We also know that Sean got obsessed pretty quick, so maybe, a little later, when Hailey cloned his phone, he cloned hers. And he, or someone he's connected with, has been screwing things up ever since.
It makes sense in some ways that he has connections somewhere; that's likely a techie. I don't know how else he'd be able to get not only Trudy's home number (Most first responders, in my experience, are told not to list their phone numbers) but also Hailey's personal cell. And maybe it extends further. He could have found a way to monitor her emails, and even her snail mail, at least at the apartment. Sean could still be pulling those strings from behind bars.
I'd have someone Jay was working with in Bolivia be home on leave and drop Hailey a letter in person at the district. In it is Jay asking what the hell is going on, only nicer and a little more self-deprecating because he knows Hailey has a right to be hurt). He'd explain his side of things, the unanswered calls, texts and emails, to Hailey's great confusion. He'd also include the number of a burner phone picked up in Bolivia because maybe, maybe something got screwed up with his.
Suspicions raised, Hailey also goes and gets a burner and calls the number. Badabing Badaboom, Upstead is back in touch. But they're on high alert, so Hailey's still acting the part of the wounded left behind in public.
In the finale, I'd have Hailey get hurt. Whether that's kidnapped or just injured, that brings Jay home. Either to help find her, or just a hospital reunion. If it is Tracy's last season, maybe they'll go off and establish their own contracting company that offers basically the services that Jay is doing now in Bolivia.