They have to work around freight which seems to be around 9-10 pm when passing through Hickory westbound.I was presuming that two trains would lay over at Asheville and one at Salisbury (or Charlotte) since doing that would allow you to have a WB train get in before mid-afternoon without having the first morning train leave at an obscene hour.
That being said, three sets for three round-trips on this route also feels a bit on the weak side in terms of equipment utilization - I'd expect that you could get four round-trips with three sets or do three r/t with two sets without too much trouble if you're ending at Salisbury. If you go to Charlotte, that's a bit trickier (and on the "spares" front, I presume that NC would ultimately have a larger equipment pool in play between this service, Wilmington, the Piedmont service, and anything else that proves to be interchangeable).
They may want to coordinate with the Crescent for the southbound Crescent which is 1:27 AM in the morning. The northbound is 6:17 AM for the Crescent and 7:28 for the Carolinian. With a Piedmont at 8:19 it would seem Amtrak not making all of those connections without some waiting but Asheville is a national tourist city so making the connections just work for NC residents is not the complete answer it would seem.
The view of The Loops is part of the appeal and an overnight train is not going to scratch that itch but it would help with the Crescent and Carolinian.
It is going to be interesting to see how it all plays out. Just so happy to be moving from mere speculation to "it just might happen."