I don't see a full 13-4 happening but I can buy a 13-1-3 if incumbent demands force Underwood to take Rockford. I can also see the usual 14-3 if IL dems are happy with seats in Chicagoland without Underwood taking Rockford.
After that you can draw a 13th Likely D seat downstate from either East St.louis to Champaign or Champaign to Rock Island. Then a swing seat can either come from Champaign to McClean or Carbondale to Decatur.
Also for the East. St louis swing/ Likely D seat, Andy Manar wouldn't be a bad recruit. He's a fairly standard Democrat(voted for the Fair tax stuff) on every issue besides some gun stuff.
Agreed with former State Sen. Andy Manar being a good choice for that ESTL seat. State Rep. Katie Stuart (D) could be another good option for it.