I'm a little curious about how offseason improvements(or drops) actually function...I've never really tracked them closely:

1) I assume WE and potential factor in, but what else? Does the practice plan still have effect?

2) Can IQ improve or degrade between seasons?

3) Is there a breaking point WE-wise for offseason drop/improvements? Is it as simple as 40+ WE will improve, 40- will slide, or is it more complicated than that?

4) Does stamina drop more than other categories, or am I just imagining things?

1) The practice plan has no effect.

2) IQ will not change

3) It seems to me that it is around 35 but it is pretty random.

4) I've not noticed one skill increase or decrease more than any other

stats from my d3 roanoke team:
Jeffrey Pabon, junior-->senior, WE 56, improved 10 in offseason
Frank Steven, frosh-->soph, WE 28, down 2
Charles Brown, jr->sr, WE 52, up 7
Stephen Iser, so->jr, WE 23 down 2
Bill Nyman, so->jr, WE 60, up 13
Peter Figueredo so-->jr, WE 28, up 2
Gerald Peters, fr-->so, WE 34, down 4
Travis Rowe, fr-->so, WE 43, up 5

...Clearly it is not tied only to WE.

Perhaps work ethic and also what potential you have left?  If a guy has a lower work ethic but several areas still having high potential, and another has a similar work ethic but only areas with average to low potential, then he has not as much potential up and more potential down to happen in the offseason? 

1) I assume WE and potential factor in, but what else? Does the practice plan still have effect?

Work ethic is absolutely a very significant part. Now, that doesn't mean that every 65 we guy will go up a bunch and every 25 we guy will go down a bunch, but it increases their odds considerably. Practice plan has no effect. Potential certainly plays a role in that if a player has high potential in a category he has a lot more room (and thus likelihood) to improve, and if he's capped out he's not going to be improving.

2) Can IQ improve or degrade between seasons?

Nope.

3) Is there a breaking point WE-wise for offseason drop/improvements? Is it as simple as 40+ WE will improve, 40- will slide, or is it more complicated than that?

No finite breaking point. Just a sliding scale that increases/decreases chances.

4) Does stamina drop more than other categories, or am I just imagining things?

Yes, stamina drops more than other categories. I think this is stupid (and fits into some of the stupidity currently surrounding stamina in general).