Oh god! I've been asking for some of the things you mentioned for a decade or so... I just wrote an huge reply only to unfortunately delete it before posting...:/ But I'll do it again, for sure.
My opinion was always that, in order to enjoy everything PES had to offer (stadiums, faces...) we needed some kind of tool that would manage a career mode, using only PES for its best: gameplay. It would launch the game, retrieve results and stats and that's it.
Since I don't have any programming knowledge, what I did, I enjoyed quite a bit was:
- Got a full FM excel database . Studied what each skill meant for PES and FM (for example aggression on PES is totally different from agression on FM)
- Created a relation between different stats. On some, a direct conversion could be made. On others I did an average. On quite a few I had to make a average with different %. Let's say Speed is 100% speed. But Ball control could be 25% skill A, 5% skill B, 40% Skill C, 30% Skill D). Having that I'd have a table with FM values (1-20) to PES stats. Now the beauty of it is that I could adjust it to my liking. I enjoy a slow paced gameplay. So, imagine a 20 Speed FM would convert to 88 PES (the quickest players on the game would have 88 tops). But, others might prefer a 20-99; 19-98. This can be easily changed. For example, to get that slow paced gameplay I noticed that most important was the passing speed (short and long), so I used 40 for all players. And I enjoyed it but others might not. The important is what skills are on each value conversion not the scale. The scale is a user-preference gameplay.
-Having my 300'000 or so players database I had to import the stats using PESfan manually. Apparently not anymore!
To make a proper career I did the following... Simulated FM season only to get the transfers. It's so much more realistic and it's quite enjoyable to see which players your board sign (you can transfer/loan list, make players unavailable and I think you can even set shortlist targets with FMRTE).
FM also has a prestige value for each team, I'd use that to create a formula to simulate what job offers I'd get. I could start on League One, get an offer from a czech team, be champion there and sign for a Serie B team next. All of this enjoying all great stadiums from these countries, etc..
Since you can get the excel database from FM at any time, and already have the excell conversion formulas, that meant that I could easily import any youth players or have players progress.
I have to find that excel file...
This is obviously time consuming and has its flaws since I couldn't simulate games...
If we could have a tool that would simulate other games, even have a transfer market simulation... PES6 would live forever. Because everything else can be simulated... there's so many ideas on how players can impact other players (like, a player with leadership >17 would give 10% increase on all other players), better managers would improve their players stats also (for example, a good defensive coach would improve all defensive values +2 for its team), having better youth department would give you an higher chance of having better new players... and so on.
You mentioned being able to create random new players. This is GREAT for a youth system for a career mode, for example. If we have a database where you could have average ratings for each country, we would see, for example, 18 yo argentinian players with 62 average, portuguese 61 average rating and Botswana 41....
I think we could do something great. I know this is far away for now... but there's great minds here, with lots of love for PES6...

I mean... Sensible Soccer was in a diskette and had almost unlimited teams, job offers and basic transfer market. And lots of people still love it.