If you want to call it extensive knowledge, you are right i do have that. Let me explain why I believe there is a lack of knowledgable coaches in the english community and why this is partly the cause why there are no great U21 players available to pick from.
At the beginning off Season 9 there was a discussion, started by the current England U21 coach, asking us to look for, buy and train U21 prospects. On a few occasions he even posted them on the forums. I thought it was a great idea and I started scouting english players. Every 2-3 days I had a look for 18 and 19 year old english players. I noticed a few things. One, the players were or not good enough to be trainable or/and the prices that were asked for these players were way too high. Most off these players were not sold and clearly not being trained. Than later in the season, the players were relisted again, again at a way too high price. We do have a few trainable players that are drafted every season. But as I am sure you know, the only real way forward is to start a 18 year old player directly after he is being drafted. A 19 year old player wouldnt really make a difference, neither would a 18 year old player that wasnt trained for like half a season. Perhaps if he is a real cracker, you could train him, but how many real crackers do we have?
I wont give you names, because I dont have any. I dont have an excel sheet at the ready right now. But have a look at the draftees this season, just not in england but overall. I dont have exact figures and cant prove it, but from what I can see, the players with high potential are almost all 19 year olds and very few are interesting enough to be trained to become U21 players. With the 18 years it is even worse. Barely any 18 years have higher potential than all star and look at their salaries. Very few have a salary higher than 4500. With other words, very little potential among the english players, than combine this with the other problem I described before and I am sure you can see the overall problem.
That is why I would like to be proactive and contact coaches with interesting U21 prospects at the start off the season and suggest to train their players or else advice them how to sell them, at a fair price and not too high. This would help the U21 team because the player would most likely be trained and secondly you dont loose time with the players being trained.