Student in Debt,
It is not about a name change. EK only had FOs- no SOs. Yes there is a higher training cost in using FOs as augmenting pilots, but you get a safer operation. In three pilot ops, EK went to TWO Captains and 1 FO, as certain states demanded that you always had a captain in a seat. So in summary FO is safer than an SO but is also more expensive, which is why Qantas et al went down the SO track.