The player generated content from the architect entertainment system which was implemented in CoH did not really turn out exactly according to the dev's vision for it. There are 2 reasons why:
1) you could gain loot/xp/etc. which was valuable outside the AE.
2) people will always find a way to gimp a player-made scenario to give reward out of proportion to effort (see point 1)
3) (and I never see people bring this up) The amount of space each player had to upload a mission arc was WAY too limited. My bf made a lovely story-driven mission arc with multiple parts, interesting writing, custom NPC's, etc. And he was constantly having to tweak it to 'fit' in his 150k allotted space, every time they changed anything about the AE files. And really, he had to cut out a lot of good content in order to get the story arc to fit. This small size greatly encouraged the use of only small meaningless missions... you couldn't make a supergroup oriented mission arc for your super group with any depth to it, you were encouraged to make a quick little mission and that's all you had space for... and farming was a surprise? pffft.
If CoT implements an AE type system... please (pretty please with sugar on top), do not let it be little more than a farming machine. Give it the depth to let players make really interesting arcs, and prevent it from having XP & loot benefits on par with regular CoT content. Yes I know less people will use it if it doesn't reward well, but if it does reward well, then kiss your expansive game world and varied content goodbye, as people mindlessly flock to fast-track repetition, and then get sick of the game.