Scratch 15 :
The issue of command at CX has been discussed at length elsewhere. You have the deck stacked against you if you want an early command in Cathay. Some here still see it as jumping the que. The pass rate for DEFO freighters who apply is very low, between 5-10%. Taking into account those who are CAT'B'd (unsuitable for command) and those who get the course but do not finish. Also there is not too much advantage financially to upgrade on the freighter. If you upgrade early you will be on the freighter (as command) for 6-8 years or if expansion stops.....well there are no guarentees that you will get back on the pax fleet. Granted not too likely in the next 5-10 years.
If you do upgrade early because there is a freighter base closer to home or for ego or whatever, then great but it is by no means an easily accomplished upgrade.
Cheers