How about from time to time an extra quest something like event occur?
This quest should be the same for everyone and reward and difficult of the enemies should be tier based.
Also to make it more interesting a background story is good idea, plus with time limit...
For example kings doctor needs this herb it can be found there bring it, you have 2 days before kings sister die from the illness and the reward will be one of these items...
Ok my story sucks but look the general idea. And choosing from equal prises the best for you is something good also...
And will give extra work for programmers...
