The OPs Question: so what does it take to do an escort mission right?
My Answer: You have to make a good companion character. That is, someone the player finds useful and does not see them as a liability. The easiest way to do this is to make them super powerful and be escorting you. This is what is done in those reverse escort missions. Short of that, you can give them unique abilities that will assist the journey, and ensure their AI does not make them suicidal - that's really the gripe of an escort mission. Bioshock Infinite is a great example of this. But a more emotive example is what you see in a game like Ico, which is a game-long escort mission. The NPC gets just a few meaningful mechanics: saving, but more importantly, being led by the hand, which creates an emotional connection, that makes them useful in a way few NPCs can be.
But if you're doing one mission, the quick and dirty way is to have these escortees have some boon that makes the player like having them around. Perhaps they have a special horn that wards away attacking animals. That's why they're so valuable that they need escort. Perhaps they are able to patch you up well in the midst of combat. Perhaps, since you're talking proc-gen either of these, alternately.
You can do a lot to make sure your escort is not liability, but if they don't prove useful, they become quite tedious. Having unique rewards for these missions may be a thing, but even that will get old after the 100th one, I think.
