Your comparisons with Emirates, Etihad, and Ethiopian and how they operate and suggesting that a Nigerian carrier should do the same are missing one vital point...................those airlines exist on transfer traffic and the airport facilities are geared up to handle massive transfer passenger flows quickly and efficiently. This policy is supported by the Governments, the airport authorities and the police/security, customs and immigration.
As yet they don't have anything like the point to point traffic that Nigeria enjoys. If there was a will to develop a viable transfer product at Lagos or Abuja, and the Government, Airport Authorities, police/security, customs and immigration joined in positively to make it fast, reliable and easy then the Nigerian Airlines would have a major advantage in pricing as the greater point to point traffic would help subsidise the transfer traffic.
On their own and without political buy in from all involved parties the airlines will not be able to develop a transfer hub in Nigeria. VK was trying to do this but never had the fullest support as other interests wanted the domestic operation out of the International terminal. Always obstacles were placed in the way and the idea of making it easy for passengers to transfer was furthest from the thoughts of anyone outside the airline.
Transit Without Visa? Not a chance, passengers had to pay for a Nigerian Visa even if they were not wishing to enter the country.
International Transfer passengers able to remain airside and not clear through Immigration? No way, they wouldn't need to buy a visa if that happened!!
Transfer Baggage Area airside? No way, Customs have to see the bag even though it is transferring onto another flight to another country so it has to go up with all the other bags.
I could go on but this gives an indication of the infrastructure issues that need to be addressed before anyone can think of becoming an Emirates, Etihad or Ethiopian. The airline and aircraft is only a small part of the problem.