God, there is a lot of statistical nitpicking that goes on here. If we're allowed to choose time periods for our players, do I get to choose young pre-injury Waqar, arguably the greatest fast bowling phenomenon of all time? You know, the one who took 180 wickets in his first 31 matches at 18.78 apiece, strike rate 35.6 with 19 five wicket hauls? Also, I choose late-career Stewart who was indeed a very reliable keeper. I'll have a young Neil Harvey and SRT too, cheers
You're thinking about it wrong. Pre-injury Waqar was still a Waqar that was essentially a fast bowler. Neil Harvey and Tendulkar were both batsmen throughout their career, as well. We're not picking someone at their peak - we're focusing rather on player role.
Example A:
You pick Wilfred Rhodes. A player with the stats of an all-rounder who was never able to do well with bat and ball at the same time, and never really played as an all-rounder at all. Just because over the course of his career his stats equal out to those of an all-rounder, doesn't mean he can be used as an all-rounder here. As a result of this, you've either picked yourself a strong opening batsman that could be a good option as a second or third spinner, OR, a superb spinner who batted at 9 or 10.
Example B:
You pick Alec Stewart. Throughout his career, he showed that he was a more than capable opening bat, as well as being a more than capable middle order bat. Without the gloves, he would be capable of batting anywhere in the order. However, because he never really consistently opened and kept at the same time, he should not be made to do so here. As a result of this, you've either picked a specialist opening batsman, a specialist middle order batsman, or a middle-order wicketkeeper-batsman.
Example C:
You pick Garfield Sobers. A player who consistently performed with bat and ball throughout his career. However, at the beginning of his career, he was brought into the side as a bowler. Because of this, you've got license to use him as the specialist bowler he was when he was brought into the team, if you so wish. You'd never want to do that, but it'd be an option.
See what I mean?