While I like your idea as a whole (similar things were discussed in an old thread
http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=582436&page=1)
I am unsure if rewarding players the full experience regardless of how they solve the issue is the best approach. I am on the fence regarding players getting more experience by solving the objective in a more difficult manor vs an all roads lead to Rome approach where they have the freedom to solve it as they like and will be equally rewarded for it.
Would a combat encounter count as an objective?
Would you still get xp if you snuck past them?
Could you double down on objectives with multiple solutions (IE for your diamond example. Steal the diamond, turn in the quest, then go back and kill the previous diamond owner.)
Would you gain the same experience spelunking an ancient cavern to bring back some ancient relic vs passing a speech check to convince the quest giver it doesn't exist. (Extreme poorly designed quest)
