As for realtime caravan driving/protecting... there is no mod I know of that does this. It would be nice to see.
For the second part the closest I can think of is a mod wich name is currently beyond memory, but someone here may remember it, it{s from years back, and I think never made it past beta, the concept was replenishing quests, sort of the radiant system skyrim uses... there were five tipes or so...
-Getting a particular ítem for a merchant (any merchant in the game could hire you, sometimes any ítem of the kind would do, but others the ítem would be special and located in a random chest on a random house, The NPC would tell you the aproximate whereabouts of the ítem requested)
-Creature bounties every week
-Monks that would administer oaths, and send you on pilgrimage to a ruin or tomb, wich you would have to clear and rest to fullfil your oath (the script would take into acount if you broke the oath for example if you toke an oath of silence and talked to someone it would inform you that you had failed the quest)
-alchemists and witches on the wild would ask ingredients in Exchange for rare potions
Those are some examples... cant remember the name, but I do remember that it made use of a scroll as a quest journal, since by nature it would fill up yout game journal with pointless entries, hopfully someone here′s been long enought to still remember it and maybe post you a link to it.
There are others atempts at job mods, there are a few PC owned shops and inns, the East empire post office mod or something like that, lets you carry packages to various destinations (think it was covered in the Mod showcases by darkelfguy), and there were others im sure.
Actually I′ve just remembered there is also a mod wich allows you to be a trader, and actually implements a district size economy to Vvanderfell where you can buy goods at variable prices and then look where to sell them for the biggest profit. (name also escaping me).
Hope someone else may clarify on this!