'I'm a vault city citizen now! Hurray! Oh, wait, three quests and thats it?'
'Oh boy, I sure killed eleven people in here. Bawww, my reputation is -7000'
'I like collecting shrubberies! :3'

As you join a faction or a city (cities are factions too right? nevermind) you are given some tasks daily or in some smaller amount of time. The quests are small favors selected randomly every time and could be something like: bring us a cow (or a shrubbery!), bring us a 10mm pistol (or a M72 LAW anti-tank rocket launcher!), some kind of armor, some ores, alloys, parts, anything random + random amount. Of course not some preposterous combination like 20 tesla armors. 1 armor/weapon, 1-7 resources/craftable items. If you complete the quest you are given some positive reputation in this group as well as some small but suitable amount of xp.
The second idea is that with every favor like this or
http://fodev.net/forum/index.php?topic=1285.0 you gain some trust and level up socially. Eventually you get higher ranks and evolve from recruit to idontknowwhattowritehere etc which enables you eg to use crafting stations, special faction vendors, lockers, rooms, etc.
All this would be a nice refresh from constant farming and grinding, sometimes you'd be like 'hey! maybe searching for this item would be more fun than killing scorpions all day :3'. I don't know, it's just my idea, because sometimes I think this way and make myself some roleplay quests in this manner, and there are not so many quests ingame. The random particle makes it more rougelike and can surprise you, also its not so hard to do I guess. One npc in each faction would give those quests and the rewards.