No, it's not a direct swap. The flanges are different, the 603 uses a T3, the 602 uses a smaller TB-025. Both are set to 12-14psi of boost. If you put a T3 on the 2.5T, you would likely end up with significant turbo lag, although peak power could increase if you also have the injection pump modified by Myna. This would result in a car that was a real dog until 2500rpm or so, then it would be pretty quick. With the stock injection pump, I think it might be a waste of time to put a T3 on a 602. And it would definitely not be a bolt-on.

What is "lots of play"? The turbine shafts are supported by the oil film, they will normally have a noticeable amount of side to side movement. But it shouldn't move in or out much at all. These turbos don't often fail, other than the shaft movement, why do you think it's bad?