Whoever makes a JJBA mod with everything would be my new religion, I mean it’s like the best manga/anime ever for me. Furthermore, I think Stands, Hamon/Spin, Stone Mask & Pillar Men related mechanics would be quite challenging to code, especially if ,by a holy miracle of Christmas in the middle of July, this mod would allow you to create your Stand from A to Z rather than just using already existing Stands.
This being said, JRMCore is clearly not adapted as Negative brought up, and knowing how various Stands power/appearance can be, it would require a totally new core mod. So I’m far from underestimating Jin’s skills at coding, but I think the tools he has right now are not adapted to JoJo. I mean any manga involving training would be fine, but there isn’t at all, except maybe for Hamon but it doesn’t go far. And last but not least, he already has so much to handle, nah it’d better if he focused on one mod at time (still he does as he please).