There should be more districts going into Chicagoland, but you are on the right track.
You can already draw 2 Dem seats downstate (the 2 squiggles). You can't really get up to a 15-2 map without far worse boundaries and annoying a lot of incumbent D congressmen.
I was trying to say what should happen (as egregious as possible of a gerrymander should be drawn, and if it gets struck down for partisan gerrymandering, that is win-win), not what would necessarily in fact happen.
I wouldn't trust that downstate Dem districts will necessarily stay Dem - it is safer to draw them into Chicagoland than to assume that they won't become more Republican (in particular Cheri Bustos' district).
You can draw 15-2 though, i.e.
https://uselectionatlas.org/FORUM/index.php?topic=294399.msg6543428#msg6543428