Yikes. I don't think I have what it takes to create it. lol
You'd be surprised. The stuff you've spelled out here can be achieved using that Hacking NBA Jam TE
document and becomes reasonably "easy" once you get into a groove with the portraits and setting up the stats. Plus, there are editors on this site for changing player names and stats (both visual and in-game). It really is more time consuming
than difficult, and once you get into it, I'll bet you'll find other things you'll want to do, like edit some of the text regarding features, or change names in the roll call screen...
There are websites that can help with stats too. NLSC
has a forum regarding basketball videogames, so you could get some ideas (and likely a fanbase) there. There's also a 2K-like website that doles out a bunch of stats for many players, so that could be leveraged too.
Again, all do-able. It really ends up boiling down to a question of how badly do you want to be able to play that game (considering the time commitment making it), or how many downloads are you expecting, and are you willing to put in that much effort to get them, even if the base of interest is fairly small?
If none of that motivates you, take a look at this [shameless plug!!!] romhack
. It incorporates just about everything I learned through writing that hacking document, and that hack came about with a good amount of help from some great folks on this site.