So, here's my thoughts on Mikuru:<br/><br/>Mikuru has information from the future, but she's been informed of the certainty that her presence alters the future.  (except if it doesn't...<em>dun dun dun</em>)  If Mikuru is altering the future, then her main priority is to keep her existence from being a paradox, such as by allowing humanity to go extinct, or keeping one of her ancestors from breeding.  On the other hand, if she's in the time she is via predestination paradox, then she can take comfort in the fact that her actions are more or less set.  (though she may be uncomfortable if she has to become on of her own ancestors)<br/><br/>Mikuru has likely traced her genealogy back to the 20th century, and researched all extinction and dark age inducing level events that threatened humanity during the period she was sent to.  Like McCoy in Star Trek IV, the Voyage Home, she may be simply amazed that humanity even survived.  (actually, if you haven't seen that movie, it's a good way to get a perspective on what people from the future traveling to the past to correct a timeline error is like)<br/><br/>Haruhi is a glitch in the timeline, and the most important danger is that she could collapse the space time continum.  (likely by turning the planet into closed space, although it's possible Haruhi has temporal powers as well) Mikuru has three main possible avenues of getting information from the future; memories of the future that automatically update when her actions change the timeline, communication with the future, and other time travelers.  Memories are very simple, but they imply that Mikuru will have bad bad things happen to her if she becomes a paradox.  Communication with the future is highly illogical, but could work if changes in the timeline propagate slowly.  (otherwise all of the consequences of Mikuru's mission would have already happened.)  Finally, the future could periodically send back other time travelers to keep Mikuru informed, which has the advantage of locking in the information in the time stream.   This could be simplified by making the time travelers projected holograms only, which only Mikuru can see.  (in the style of the American TV show Quantum Leap; the main character was aided by a hologram equipped with a computer which calculated the odds that the main character's actions were having an effect on the timeline.  When the probability reached 100%, the changes propagated to the future)<br/><br/><br/>As for Ituski's powers, Ituski has very very minor powers 90% of the time and is a god in closed space, likely surpassing the power of Yuki.  However, he also knows that closed space is dangerous to the world, and strives to close closed space when he can.  He can keep his powers up to a minor level in the club room, but simple balance of power suggests that Yuki and Mikuru would be using their reality altering powers and future theoretical physics to keep the club room fairly mundane.  (letting a telepath around someone who can destroy the world with a thought seems like a<em>really</em>bad idea)  It's more in keeping with the character, if he's going to send secret messages, to text message people and possibly try to use his "second in command" status in the SOS brigade to initiate private conversations.  Ituski usually only resorts to his powers when it's the world on the line.  (as indeed, all of the characters except Haruhi do.  I've further limited Yuki's powers by giving her a belief that each change in the world has to have an equal and opposite change, although this can be paid very gradually.)