YHZ-BOS already exists on Business Express, owned by American Eagle.
Saskatoon???? What???? I don't think so. Right now the only transborder flights from Saskatoon is the NW route to MSP, and it's only 2 flights a day. I don't see AA/AE going after that, at least not until they fill in YWG or YEG.
YWG-ORD-DFW has potential, but like they say, seeing is believing. As to YEG, given the geography involved I think (just my opinion) that an extension of YYC flights would work. They could fly YEG-YYC-ORD, and connect passengers from that flight onto ORD flights. They couldn't carry YYC-YEG passengers, but it would allow them to run planes at reasonable capacity, and they would have the competitve advantage of have US clearance take place at YEG, even though they would still require a stop at YYC.