My experience with AA, with my open-dated M-OWE is that they will just book me into connecting segments. The original airport will give me a BP with hand-written note of the ticket number, sometime with the word "invol route change" or things like that. The original paper ticket with go with the 2nd segment (connecting airport).

but:

1. I am holding a hand-written ticket, as GB said, they don't want to mess up with that.

2. I am an AA EXP, traveling AA on AA-stock OWE ticket, and AA rebook me to AA but not another airline.

3. When you do the reservation by phone, the booking agent may hesitate to book you, but I just insist that I need resevation of certain sub-class with a ticket number, they will do it anyway.

4. and yeah, the res agent will always said "booking is confirmed subject to ticket verification at the airport", sounds scary but as long as your paper ticket is valid and with the right sub-class. I am ok.

Good Luck.

Oh, BTW, at least for AA, if you do your segments reservation into different records instead of 20 at the same time, it actually helps to check-in faster for me, although it create a tough time when you talk to the RTW desk.