I think that there are a few changes that would be VERY easy and would improve the game (some are repeats of what others have said).
The minimum four day contract limit is great, make it longer.
Salary floor is great, make it higher.
The players in draft are too poor shift the median up a bit.
Here is two suggestions that may be medium hard:
Shift the sliders up a little to make the 2/3 zone better and the LI offence worse.
Finally one that is difficult:
"Naturalising" players. Once a player has been on your team for at least six consequetive seasons they should count as a drafted player for all fan based benefits even if they are of a foreign nationality.