"a bunch of one-ways through the operating airlines" implies, to me, not a single ticket (from anyone), but a bunch of individual tickets.

A bunch of individual tickets would be just that; carrier N will hold no responsibility for you if flight N!=1 is messed up. Interlining may tag your bags through on a good day, but no liability attached. Since the second last time I checked a bag, AC was itself unable to check a bag through YYZ OSS correctly, I hold out little hope for a random GA managing >2 hops.

A 3rd party TA might be able to link together on a single ticket a bunch of one way hops, but then any problems change from the carriers laughing you to ignoring you, at least long enough you are stuck in South Outer SH International overnight.

As for getting the ticket from AC? Call in and expect to HUCA