I'm kind of torn on this suggestion; City of Heroes, another long running MMO included publishable custom arcs, and I worked on an arc there for a good number of weeks... to both good and bad effect, and experience.
Firstly, I think the initial post quite usefully suggests ways to avoid the inherent pitfalls that initially made me cautious of the idea.... In CoH any quality arc was rapidly buried in popularity under the "farming" missions, which gave the best rewards or per-time experience growth, because that's all the majority of players cared about. Sure the role players loved the design system, but the power gamers outnumbered them, outvoted them, and their well written work got shoved further and further down the list into eventual obscurity, from the barrage of 5 star votes for fast levelling missions that were literally often a an auto-completing mission that you entered and it gave you the reward. It got so bad the Devs started banning any arc which even had the word "farm" in their description.
However if the player has to donate the reward themselves, this at least takes the farm element out, as the reward has to be earned by someone else legitimately first. And who is going to bother to set up a simple mission to just complete a transaction a drag and drop could do instead? The people who make missions are thus more likely to care about what they write, and that is a good thing. It would also allow more player-run competitions without the questions about unfairness involved; the first person to genuinely kill 50 ettins or whatever is going to get the prize, rather than the one who only got it because of promises of teh cybzoring or whatever....
Now myself, when ever I go to an IDOC, I look not just for rares but the player written books to collect, because there are some fascinating stories out there, and it's good I feel to get a sense of player-created history. And it was the same in City of Heroes too; there were some true player written gems out there... and what's more, if you are open to honest community feedback, you can polish them to almost perfection over time. I went through numerous drafts of my own arc, tightening the plotting, tweaking the spawn difficulty for other character sets I may not have considered... because unlike the EM's arcs, I didn't have to finish my a certain date to advance the plot.
However... and this is where I have reservations again... don't believe that the shining gems are going to be indicative of the full experience. There is going to be a tidal wave of absolutely rubbish arcs, because frankly despite everyone having some true worth, that doesn't mean it's always going to lie in writing gaming events. And that goes even for people talented in other areas; CoH invited guest authors in, like Scott Kurtz, but the few I played just weren't very good, because their skills in webcomics or fantasy authorship don't necessarily transfer across to the gaming environment. Be honest, how many of you in any MMO really read the textual flavour of a mission, and just go straight to the Kill 10 Creeps part? That's just the way games are, we get the main pleasure from the gameplay itself.
And the vast majority of content is going to be from mediocre writers to start with, or people relying on their own in-group in-jokes, or worse just outright ego stroking ("help my character be awesome! oh, and hit a few things yourself if you'd like"). Then there was the theft of ideas and designs and even people trying to claim credit for writing your arc... It's simply a myth that the average person, when released from external restraints is going to be a creative, constructive, sharing individual. Quite the opposite, I'm afraid.
I've done some other game-modding myself, and the same goes for the audience for this stuff; and as can be witnessed here on this thread. For every person who says "Whoah, great idea" (and I do think this idea has a lot of merit, as some thought has been put into how to avoid game breaking issues) you'll get 10 people being jackasses and trying to cut the clear sighted down to their size. I once released a game mod for Warhammer: Dawn of War which used the gretchin builder unit to set up mass runt on runt battles... but the AI was flagged deep in the unmoddable code to only ever build with it; the Read Me, the file name, heck even the pre-match level description warned not to try and use the default AI with it... and for nearly a year someone obsessively spewed hatred onto the hosting webpage, screaming at first "it doesn't work!!" for single players with no friends, and then tried to personally abuse me when it became obvious it was their own stupidity was the problem because he'd not read any of the documentation at all. So expect the same in Ultima Online too, once your missions get outside the realm of your close knit group of sympathetic friends. The world shouldn't be like this... but sadly it is.
And I just want to stress here, and not out of arrogance, that my work was damn good. If you bought Dawn of War: Winter Assault in Poland, a map I worked on with another chap was selected for and included as part of an unlock code on the publishers website. But do you know how many people took the time to email a "great map dude!" comment? Absolutely zero. Got a few bug feedbacks, and still do occasionally on the public host... but this leads into the next problem. The core code is constantly changing too. What worked back in 2004 doesn't work now, not just because they kept patching the original game, but because they've added expansion after expansion, and the map wouldn't work correctly in those games unfortunately. The idea of trying to script an event for an MMO like Ultima Online, with it's 13 years of spaghetti code, multiple clients, massive variety in templates etc... well it sends shivers down my spine, frankly. Even "Kill 50 Ettins" is going to be more complex than you'd think; are there actually enough Ettins on the server to do that in a reasonable time? What if everyone's going for them? What if someone who hates the author is griefing the event...?
You can avoid that some of that problem if it's just kept as a quest book as the OP stated, because you could set it to not be copyable, and only sell it from vendors in places gits are banned from, or just give it physically to people you like. And good will from friends will perhaps remove any potential bitter feelings... hey it's all fun between friends, right?! But it will still require some thought on the author's part... EMs have far better tools than we do right now, and they can even spawn what they want, but how many of their events go to plan? And what if they didn't know before hand, which we do now for example, that the drop rate on something like the gypsy moongate jewelry was only 1 in 25000...?
So... basically, I do agree with the OP. I share his sense of appreciation for the art of creativity. I'd be glad to see more support for player run questing in game. I just have a lot of reservations about the reality as we'd end up experiencing it...
