The character list of the first link is just the JUS roster. I doubt that they wouldn't add the popular characters of the last 10 years.
"Everyone is here" in a jump game has very different context that in smash. Everybody from the magazine? Impossible, and dumb, no one wants to use resources to adapt waqwaq, barrage or zombie powder and those are from big authors. The 100+ hits of jump are built on top the dreams of 500+ newbies (and authors failed series).
So then everybody from jump crossover games? There are a few from the Famicom ones that were in that wouldn't make the cut now, as they were mildly relevant back then and just a non issue now, the Roys of the roster. You can have only one or two Roys.
Then there is the biggest and most controversial Roy. Buso renken. Even if shueisha is willing to keep using kenshin, I doubt that they would bring back the Roy of JUS on top of the watsuki controversy.
Finally if Takei wasn't invited, or didn't provide a page for the wall of 101 congratulations on the 50th anniversary page, and with Shaman King continuing outside shueisha, I doubt we'll see any SK content.