Clearly all the Nadia plot. All of it. You don't get a choice about that. And I'm sure Lachlan would like to express Luke's appreciation for Cassian's heroic sacrifice. And obviously there's also Jules for spying that turns into friendship. Aaaaand Alan, since he's his boss now (sorry about that). And ALL THE REST of my Camelot plot, which is too bountiful to really even list.
As far as spying goes, he's more than welcome to any of my Resistance kids, too. Francis, maybe? Or, you know. Clark. If you want that Star Wars connection too. Or any other suspicious figures he'd like to spend some time watching.