Air Nigeria has nothing to do with Nigeria Airways. The latter filed for liquidation on July 31st and the employees haven't been paid since. Flights to JFK, LHR, JED, DXB, and african sectors continue to operate, however.
The Air Nigeria project is a joint venture between Airwing Aerospace Ltd. (Nigeria) which is affiliated to Airwing 2000 at Coventry (leasing firm) and the Federal Govt. of Nigeria on behalf of Nigeria Airways (which is shouting foul over its non-consultation).
The route structure needs a B747-400 (long hauls to JFK and DXB), while the A310-300 could be used on thinner long routes. 737-400s are clearly targeting domestic sectors and West African routes.
It seems the faceless Nigerians behind this transaction are stressing that 'modern' aircraft should be deployed, perhaps appeasing the Nigerian Govt. and justifying their rip-off purchase of Nigeria's entire Bilateral Agreements (Which is why Nigeria's privatization agency BPE is against Air Nigeria).
If there is a will, there is a way