Speaking of that option, the one to re-unite the two of them. It reminds me a lot of Cyrano de Bergerac...but that would fit more if the "dear john" letter content romance exclusive. Do you think you'd have this story arc only available to PC's who had engaged in flirting? Meaning, that the companion character would only ever open up to someone who'd shown that kind of interest?
I'd have a Dear John story arc open regardless of romance, because the character arc would be enough to largely dominate a character's unique plot budget. Moreover, helping someone deal with long-distance relationship troubles is a wonderfully fertile role-playing opportunity, one in which the nuances of context range widely for the countless sort of observor relationships are possible. Even 'just friends' have times when they need help with relationship issues with someone else.
If I were to include a reuniting/reconciliation angle, though, I'd frame the Dear John letter in specific ways. The obvious one being that the Dear John letter itself is the sort written by someone else- perhaps a forgery under the wife's name, or perhaps someone claiming the role of a 'friend.' Think of it as, 'Dear John, your wife is sleeping around, and here's some helpful proof.'
And if John writes his wife 'is this true,' then he gets a letter that says 'Dear John, it's true.' For whatever reasons she gives, but she confesses the infidelity when confronted.
A reuniting path (and this is hardly required) would have a context in which reconiliation is more reasonable. Something like the wife threatening divorce, or that it was an affair and not a committed relationship (though her lover may try and trick/convince John/the player that it is/should be a committed relationship). In such a case the resolution arc would focus on forgiveness (John of his wife) and working to repair the problems that started it (John being away for so long- maybe now he commits to staying home). Whereas the 'steal John' or 'breakup' paths would go along the lines of 'you can do and deserve better' or 'you'll never trust her again.'
So, as a brief encounter sketch of the major conversations-
'Friendship route.' The PC isn't trying to romance John.
1. Introduction. John talks about his beloved wife. John misses her, but has no doubts.
2. The Dear John letter (from a friend). John gets a letter claiming his wife is cheating on him. John is angry and doesn't believe it, but the letter includes some evidence or token to make it credible. John resolves to mail his wife directly.
3. The Dear John letter (from the wife). The wife writes back, admitting to infidelity. She gives her reasons, and indicates that she doesn't want to hurt him out of spite, but also says she doesn't intend to have a farce of a long distance relationship anymore. She refuses to answer or send any more letters.
4. John is depressed and angry. He gets no more replies. The PC can console him, cajole him, or take different positions regarding the wife. The player has two diverging paths to urge John to take: (1) break up, or (2) try to reconcile. Regardless, John wants to confront his wife.
5. Confrontation with wife. Before the confrontation her Paramore in the affair speaks to the PC, urging them to allow the marriage to end because Reasons, such as 'this will let John focus on saving the world with you,' but which would allow him/her to hook up with the wife. Confrontation could go many different ways, based on player involvement or prior actions. End state- John breaks up angrily, sadly but in mutual agreement, or resolved to reconcile.
6. Resolution. John has made some sort of peace. Maybe not with the wife, who he may hate, but he is resolved to move on with his life. If reconciled, John is resolved to return home and stay there after the quest is finished.
'Romance' Route- the PC is trying to get with John.
1. Introduction. Initial flirting is politely turned down. John talks about his beloved wife. John misses her, but has no doubts.
2. The Dear John letter (from a friend). John gets a letter claiming his wife is cheating on him. John is angry and doesn't believe it, but the letter includes some evidence or token to make it credible. John resolves to mail his wife directly. John is in a state of denial right now, and would ignore blatant flirting/opportunism. However, a second 'subdued' flirting path plays the role of closer confidant.
3. The Dear John letter (from the wife). The wife writes back, admitting to infidelity. She gives her reasons. If the PC has been flirting with John, one of her reasons may be that she has heard 'from a friend' that John has been getting close with other women while away from home. She doesn't want to hurt him out of spite, but also says she doesn't intend to have a farce of a long distance relationship anymore. Regardless of how blatant the PC has been flirting with him, John is more angry at his wife than at the PC. He knows he hasn't cheated (despite Sexual Tension, which he might admit to if the player has been blatant), and is angry at the wife for believing lies rather than at the PC for giving fodder.
4. John is depressed and angry. He gets no more replies. The PC on a romance path consoles him. Two flirt-related lines of argument are 'she doesn't deserve you,' or 'I am here for you.' The PC on a romance path can (but doesn't have to) outright seduce him- either by urging him into revenge sex and the unresolved sexual tension, or offering comfort sex based on trust. Regardless of whether the PC sleeps with John, he still wants to confront the wife.
5. The Confrontation with the wife. Naturally actually sleeping with John makes things much more contentious and potentially explosive. This time in the pre-confrontation, the Paramore reveals that they know about the PC's attempts to woe John, as well as if they slept together. The Paramore makes a deal/offer of mutual benefit- the two of you work together so that you (the PC) can get John, and he (the Paramore) gets the wife. Everyone's happy. If you refuse, but slept with John, he threatens blackmail and to reveal the truth. Despite this, with the right words (and a pre-emptive confession) you can still reconcile John and his wife- it might require special conditions or a speach check, but basically the PC can appeal for mutual forgiveness, though that requires giving up John. The endstates are the same: John and his wife break up angrily (much more likely if you slept with John), amicably, or reconcile.
6. Resolution. John has come to terms with his feelings for his wife, and for you. If you broke them up, then John is ready and wants to be with you. Ending the romance now... isn't very nice, and might involve some accusations about deliberately destroying his marriage. But assuming you don't, John is committed to having a better committed relationship with you- traveling with you so that you might never be apart, or settling down together (if that's what the player wants). If the player passed on love to reconcile John and his wife, John thanks the player and gives a speech about how even though he will be faithful to his wife going forward, the player will always hold a special spot in his heart forever. Maybe, in a different life... but in this one, he hopes they can still be friends.
And so it would be.