CX can print more than 16 segments. (according to some other post I saw a while ago).
In theory, travel agents with the proper equipment (excluding those who use ATB ticket stock) and use OPTAT type ticket stock (most Canadian travel agents still use them), which is the 4 coupon, multi-part dot-matrix printer feed type of tickets can do so. But then they would have to use a special software program obtained from an outside vendor (seperate from the CRS) and "manually" fill in the screens, or export a text-file containing the PNR and force it to print the ticket.
After they print the ticket, they will have to go back to the CRS (Sabre etc.) and manually type in the ticket numbers as if "manual" tickets were issued.
A lot of trouble!!