Sorry, I didn't explain myself well. What I have is direct access to Abacus through a VPN over internet. To do this you need a (very) tame travel agent who can get you the software, login id, etc. This is not recommended for the general traveller.

But still nothing to stop you making the reservations separately directly with the airline. CX, for example, can make reservations on any OW airline.

As I read the new ticketing rules, you can still just fix the first segment (which you have always had to do) and leave the rest open-dated with separate reservations. You just need to ticket economy class further in advance if you are unsure of the reservation on the first leg. But this isn't an issue for business and first.