Problem is Type that a "conventional" airframe means every Navy has to buy a conventional carrier...... and they are very very expensive. A "Harrier 3" would either look like the F-35 B (so no savings at all). or like a Harrier - in which case you'd be telling people like the USMC they had to go into action in (say) 2040, with a basic design that's very old and probably very easy to shoot down.