Hanging out in random encounters, you never have very cool terrain or buildings to hold up in, also it's not very productive. This would involve a reward.
Furthermore, in random encounters you have to wait a very long time for any decent challenge to show up. It would be nice if the reward/time ratio could be comparable to caravans, and there doesn't necessarily have to be friendly NPCs to help you. Perhaps make a very challenging one with good drops. This would be worthy PvE content.
Boss mobs could even be included on the final wave.