Done ! (and can be improved if needed) through this script (except the nrof part).

Add exp rewarder type object. It's basic properties:

  1) amount of exp to reward the player (stats.exp)
  2) Skill to award the exp to (skill field)
  3) Flag to denote we should teach the player this skill if they don't
      have it (can_use_skill flag?)  In this way, rewarders could grant
      skills to the player.
  4) Different ways to be activated (walk on/fly on, as well as it being
      activated from something that 'pushes' it (aka, magic mouth, button,
      etc)).  In the case of another object activating it, the player
      would still need to be on the space the object is on.
  5) Use the 'slaying' field to denote that if the player has a force in
      his inventory by the same name, he doesn't get the reward, and if
      they don't have such a force, we add one to the player (so you can't
      get the same reward repeatedly).  Use something like 'value' or
      other field to denote how many ticks the force lasts for.  If value
      is zero, then force never expires
  6) Use nrof to denote how many times the reward works.  Eg, if nrof
      is 1, then once a player uses it, no one else can get that reward
      until the map resets.

you can already do this through some plugins, including the Python one :)