I'm wondering if this route could work maybe 1x daily. I remember that I when I used to fly this route:

Southwest's first flight was mid morning with a lot of connection feed from the east. The flight was generally high fare and pricey, Chicago based pax pretty much had to pay for Early boarding to not be stuck in a middle seat, and Southwest's slimline seats weren't comfortable. I disliked it but I thought Southwest was likely making a lot of profit on the flight.

Delta's flight from ORD also isn't very early and it was Delta Connection actually. United and AA were flying regional jet aircraft as well.

So, while there are 4 carriers, no carriers offer a departure reaching SLC around 9 or 10am, and the legacies are just offering regional jet service, and all carriers are operating the flight with connection feed considered first.

With Frontier going away from hub model, could it overfly DEN and offer MDW-SLC? It's overflying DEN on some CLE routes like CLE-PHX. I think Frontier has enough name brand in MDW and SLC. It'd offer no connections, thus offering even lower fares for the pax from Chicago and SLC with them not having to compete for seats with connecting pax. However, there's no guarantee that the flight times would be early in the morning, but I think it could be popular atleast with leisure pax

Thoughts? I'd think if it offered it, likely one carrier would bow out and my guess is AA.