Qatar can serve the local market with a one stop via LHR with BA codeshare ex BHD or via DUB. The volume and or subsidy would need to be such that it's commercially more attractive that those current options. I couldn't see a one stop being attractive for Qatar. How would the Welsh government feel about all the crew not overnighting in Wales, where they buy hotel stays etc. Apart from that I just don't see Qatar doing it.
For NYC or BOS the only airlines who logistically for the bill are the US big 3, Aer Lingus or Jetblue.
If they have any hope its Jetblue or a designated one stop Icelandair service, which again seems unlikely. Be great to see a North American route coming back. Air Canada with Max might be something that could be attracted with the right support package...