I would look at the relationship between height and weight, this would indicate if a player is underweight, overweight or muscular for his position.also a column for preferred foot.
A pattern does exist between value and salary as well. Have you considered adding this to your analysis and find the best value for money players, taking physical conditioning into account.
I am not one for figures but prefer charts to highlight trends. Perhaps a manhattan skyline as opposed to a pie chart.
Do you keep track of their average training, by session and match. You could get valuable information as to which time of the day or season is best to train them.
I like to track their yellow cards against match formations so as not to play certain players in or against certain formation. Have you considered adding this to your stats file? The same goes for tactics?