NG conversion from classic is just a differences course. Half a day in classroom and one sim session and four sectors line training. Very little cost there. Acquiring the airframe is a very expensive exercise. So I suspect that rules out NGs.
76 from 75 conversion, very similar story to above. However palletised freight on a 76 pays for the trip. Pax revenue is bonus. If it was my trainset this would be my focus.
New uniforms and paintjobs are just a wasteful luxury. Money would be better spent on crew retention.
Oh and before I forget, NG conversion to 777 is also just a differences course. But we don't get 777s til 2008!