Are you starting from LAX or CHI? :huh: And is this a paid trip or an award trip? :huh:
First off, if starting in LAX, you are aware that the TE arrives into CHI (even if on time) AFTER the EB departs. Thus you will have to stay in CHI at least 1 night anyway! And second, if it is a paid trip, it would not matter if it was a circle trip anyway. Circle trips only come into play if it is an award redemption.
If starting in CHI, and booked before 1/24, just book a 2 zone award CHI to somewhere along the CS route and another (with a different agent from there to CHI. All connections would be guaranteed! If booked after 1/24 or if it a paid trip, it does not matter.
As said, they usually hold the TE for the CS to arrive. If the CS is very late, most likely you will be bused to play catch up.