I think hubs are great. They are very efficient. I've never heard of "channel-in-a-box". What is it and how much "attention" does it need from "existing staff" (who I assume are not MC operators)?
I've worked at stations with different hub setups. One was completely hubbed and we never really had any technical issues (at least on air) that made me think it wasn't worth it.
Another was a hybrid setup where they had local operators during key portions of the day to do MC duties, but then during overnights and weekends, the hub took over. I don't know why it was hybrid instead of entirely hubbed. At first I thought it was a union thing, but then heard that the MC operators contract had a "no manning" clause, meaning the station was free to hire and fire according to whether there was enough work to do and they weren't required to employ a minimum number of employees. So now I'm guessing the union contract would not prevent going fully hubbed.