No not off topic, nice reply.
I am not sure about what modification we are talking about, but it's true, it is probably better to modify it now, than after or during production. That's the case with every product, except when you need to offer it on market ASAP or you don't have the funds or technology to fully develop it. But R&D engineering costs a lot of time as well as money... and if you have to prolong the service life of your current fleet because of those delays, it costs altogether maybe more than if you had planned the modification for the next production batch.
However, what I understood from interviews with PAF officers, is that Pakistan is leaving a lot of things to be implemented later. And that costs more, but it looks like they are taking efforts to make sure it is ready for integration of future mods. No shame, they are doing the same with other combat aircraft. The HMS is just one of those things to be added on later...I think.
Yes, I believe the project director is right when he says the JF-17 is currently already better than the F-16 Pakistan has. It should be really, you are talking about 25-30 year gap here. Besides that the F-16As were conceived as day fighters and delivered without real multi-role and no BVR capability. Don't forget that the US has already retired quite a number of F-16As, even the reserve units are equipped with F-16Cs I think. But it has to got a decent radar and engine though...which still need to be selected.
he said that never before any airforce has relied on planing based around a single fighter and succesfully completed it as per requirements.
I don't understand that comment, because:
1. Pakistan is certainly not relying on a single fighter, as it is trying to get new fighters off-the-shelf as well.
2. I think many fighter developments/plans have actually been completed 100% as the requirements state... for some this was successful, for others not. In the last case, the problem was mostly that requirements were no longer valid.