Skywest is a regional carrier for American Airlines (as American Eagle), Delta Air Lines (as Delta Connection), Alaska Airlines (as Alaska SkyWest) and United Airlines (as United Express). They have 141 E175 with 17 on order and an additional 100 E175-2 on order.
I wonder if an E175 airline could work based in a central USA airport. BNA (Nashville). Ranges to all major airports are 2000 miles or less. The longest E175 flight in April 2019 was 1973 miles (SkyWest Airlines Inc. PDX to BNA see below), but the longest daily flight was 1772 miles( also on SkyWest).
BNA is 54% Southwest Airlines so if SkyWest were to try and compete with Southwest
It would not be running afoul of it's legacy carriers if it stays off their routes
United Airlines Chicago–O'Hare, Denver, Houston–Intercontinental, Newark, Washington–Dulles, San Francisco
United Express Chicago–O'Hare, Denver, Houston–Intercontinental, Newark, Washington–Dulles
Delta Air Lines Atlanta, Boston (begins May 1, 2020), Detroit, Los Angeles, Minneapolis/St. Paul, Salt Lake City, Seattle/Tacoma | Seasonal: Cancún
American Airlines Charlotte, Dallas/Fort Worth, Los Angeles, Miami, Philadelphia, Washington–National Seasonal: Chicago–O'Hare ]
American Eagle Charlotte, Chicago–O'Hare, Dallas/Fort Worth, New York–JFK, New York–LaGuardia, Philadelphia, Washington–National
Alaska Airlines Seattle/Tacoma
BNA to major airports in miles
PDX 1973 --- longest E175 flight in April 2019