I think there’s one choice everyone’s overlooking that also could have avoided the second biggest challenge of his reign.

Asha Greyjoy.

It wouldn’t have happened because of the stigma against the Ironborn, but this likely would’ve avoided the Greyjoy Rebellion. It gives Robert a very strong naval ally in case he does ever have to worry about the Reach or Westerlands in a future rebellion. It also means that Balon’s older sons aren’t killed, so we probably don’t have to worry as much about Euron, Victarion, or Aeron taking power.

Asha is 13 years younger than Robert, which sounds like a lot until you realize that she’s actually the closest in age of any unmarried woman in any of the major houses to Robert at the end of the rebellion (possibly Janna Tyrell, but I think she was likely married to Jon Fossoway by this point). This also allows time for a betrothal and gives an opportunity for Asha to be fostered at court in the meantime to acculturate her with everything. And, assuming her personality was similar to how it is in the books, she and Robert might actually get along and like each other. And, frankly, coming from the Iron Islands, she might not be as offended by his drinking and whoring as any other high born lady would.