Why move Trott when he's been a success at 3?
The no. 3 position is much more suited to Trott's style of play. You typically come in after 5-10 overs of powerplay and are expected to keep the scoreboard ticking over for 20-30 overs before trying to accelerate.
No-one else has had success there for England in ODIs, KP has been much more effective at 4-5, even though this is mostly his general drop in performance recently.
I'd rather see at least one aggressive batsman having a go in the first 10 overs.
Yes good point as to why you would move someone that's performed well in a particular position into another spot. My reasoning would be this - you aren't moving Trott into a position that is alien to him, he has performed very capably at the top of the order for Warwickshire and because he is a very good player I do not expect it would effect his performances by moving up a spot. The fach he was in before 10 overs had been completed in five of the seven ODI's in the recent series, suggests he's effectively been operating as an opening batsman anyway, four times before five overs have been negotiated.
Also his success has come in Australia, pitches I think that suit his style much more than the sub-continental pitches do. He likes pace on the ball, which you can generally get throughout the innings in Oz. In the WC, sides are likely to revert to pace off the ball as soon as the powerplays are done, even earlier at times. If Trott can get in while pace is on the ball, get some runs under his belt while it's coming onto the bat, it may ease any problems he could encounter against the slower bowlers.
He seems our key man in batting through an innings, letting players bat around him, therefore let us get him in as soon as possible.
I believe KP can be effective at three. Has the game to take advantage of the early powerplays and giving him the responsibilty to bat there, we may see a positive response from him. I appreciate he may have underperformed in this position previously, but now we are not as reliant upon him to score big and be mainly responsible for us scoring quickly, he may actually feel a freedom to play a more natural game.