Trying this again . . .
[firefox locks up while typing]
Trying yet again . . .
From a June 1970 report for the US 41 freeway from IL 120 to the Wisconsin Border:

Above is an image of the Supplemental Freeway system proposed for Illinois but with two freeways that seems to have died off earlier than the rest: the Dwight to Kankakee corridor, and a Quad Cities to Rockford route. At this time what is now I-88 would have stayed along US 30 from Sugar Grove to Clinton, Iowa.

Above is a map of a freeway plan with names for some of the corridors (probably not visible in the linked version), plus a possible variant of the more official CATS plan. Of note:
* Harvard - North Chicago Freeway: From around the IL 60 intersection with US 41 west, eventually running parallel along US 14 west of Crystal Lake to the Wisconsin border.
* Southwest Suburban Freeway: From I-57 at 99th Street west to I-55 near IL 126 where it would have turned into the Fox Valley Freeway
As for the variant routes:
* The east-west leg of the Crosstown/I-494 is shown extending east of I-94 to I-90
* The Bryn Mawr corridor is shown being a continuation of the IL 171 corridor. The 1971 interim CATS plan has the Bryn Mawr corridor stopping at I-90 near Bryn Mawr exit (82B).

This figure shows what some of the Illinois freeways were supposed to connect with in Wisconsin.