This idea may sound pretty stupid to you older people on this site but I'm actually only in 7th grade and I'd love to create myself in 2k and play against these people as the 5"9 person I am!!!
Modding (???=Vacant)
RED MC - ???
Changing team names up, and basically controlling the mod.
Courts - ???
This probably will be easy especially with Razor's new court tutorial but we'll just need some courts with the three point line bumped up and if possible volley ball court lines just to make it also seem more non-NBA.
Arenas - ???
As a middle school roster, you probably won't get the vibe that this is middle school when you're playing in stadiums that can fit +10k people. Therefore we hope to get a small group of people with the ability to make small middle school gym like crowd seatings.
Cyberfaces - ???
This may be hard I assume because the all the players on this game are adults and modding their faces to look like 8th grade students may be hard

EDIT: And including the top prospects in the area idea, we could also attempt to create faces for them.
Fictional Menu/Arena Logos
Obviously it wouldn't be cool to see these rosters play on a court with the 76ers logo on it so I think it'd be neat to create fictional logos for each team.
So that's all that'd need to be modded and actually I do not own the PC version of NBA 2K13 so I would only create the fictional basketball players that would be included in this since that's all I could do.
I also crafted an idea to throw competition in this...! We could choose an area/district for this mod to be based off on and using that we could create the top prospects who also play in the selected area so Deandre Ayton dude would be in the roster if we decided to use San Diego, CA!
The majority of these players will be under 6"2 and will probably stay in the range of ratings 50-80 (Because most athletes at my age struggle with what a pro is capable of) but this would also give the advantages to the stars who would be included in this roster have.
Below is a video that describes the advantage I'd like to see stars have!

So please give me feedback on this idea!!! If we continue I'd assume that hotguy2426 and any of you who want to join to help us out would be the main contributors while I'll just create the rosters using REDitor. And btw, I'll be converting this to Xbox 360 hopefully after we finish this up!