I think I should clarify the CX situation, with reference to the CX e-ticketing guide for Travel Agents (Word doc).

What they cannot do is issue an entirely open-dated ticket. Their e-ticketing guidelines explicitly state that the minimum requirement to be able to issue an e-ticket is for one booked (i.e. confirmed or waitlisted) segment, which doesn't need to be the first segment. All other segments can be issued open. So Bukhara is wrong about CX and Guy Betsy is missing the word "entirely".

The guidelines also are consistent with my personal experience. I have travelled on e-tickets from CX with open-dated sectors.