Wow, what a great post. I want give my opinion in this since I am the Center of the Universe (or so I see when I get these visions...):
1.Skill Drops After Big Injuries
I would absolutely hate if this happened to one of my players, but since this would apply to all teams it wouldn't be unfair. In fact, I think it rewards teams who go for depth instead of blowing all their cash on superstars who play 42+ minutes per game, every game. I think this could perhaps be linked to Stamina (i.e. lower stamina=greater injury risk, but this is very debatable and I'm not sure I'd agree with such a notion if I really thought about it). But this would add so much more reality to the game that I fully support the notion. We'd just have to put up with several "whining about career threatening injuries" posts every time some team got hit.
2. Hidden Potential
Again, I like this idea a whole lot, though I also agree with the criticisms that point out that in real life there can be a somewhat of a good idea about which players have what sort of potential. Plenty of players have "work ethic" questions and other issues that affect scoutable potential. But scouting potential is not perfect. I think the adjustment that really should be made is to make the Potential rating fuzzier (perhaps given as a best case potential) so that we have an idea who might have what sort of potential, but we won't really know until we start training them. After all, we need to have a few Tyrus Thomases and Eddie Currys in the game, the once-very-young-players with what everyone thought had tremendous potential but have shown much less maturity and desire to grow than expected. But of course, maybe they're just late-bloomers, which leads to...
3. Skill Boost
Another suggestion that begs for more realism, which I support. I think the way to handle this isn't to give skill boosts, though. I think there can be a hidden attribute for all players regarding maturity. Some players just take a little longer to grow than others, so instead of having all players uniformly train fastest as 18/19-year-olds with skills growth tapering off after 21 years, maybe some players have their peak skills growth shifted a little (perhaps reaching more trainable age starting at 20, 21, 22, 23...). And training rates could also be a hidden attribute, similar to how training rates decline now each season depending on potential, but having training rate increases for players who reach training efficiency peaks after 18/19-years-old (increase rates should be steeper than decrease rates, which may seem like a skills boost).
But also to add reality to the notion of a Skill Boost, I think there should be (somehwat random, perhpas related to potential/trainability) skill boosts for players who did not receive "training minutes" in games to account for those players who maybe had the occasional good practice or work-out. In reality, that's a big part of how we sometimes see real life late-bloomers, players who don't get game time minutes, but who stick with the team and have good practices. There should probably also be some of these (somewhat random again) skill boosts that take place during the off-season processing to account for off-season training that may help some of the (mostly younger) players.
4. Ricky Rubio Pros
In my opinion, 16-17-year-old rookies should only be players who will reach their potential sooner than other players. How much better was Kobe Bryant at the age of 28 than he was at the age of 21? He was better, but by how much? Kevin Garnett, another prep-to-pro, again how much better did he get from right out of high-school to the age of 30? I think these sort of players just matured faster than other players (see my comments on the other issues above), which is why folks think players like Ricky Rubio could even be ready for the NBA at so young an age.
UcanUwill, thanks for getting this thread started. Gets the creative juices flowing.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!