Leeds Approach,
You are looking at this project far too simplistically. Population does not automatically mean people will use it.
Just look at BHX, huge city on its doorstep, huge industry areas, easily accessible to millions more yet handles just shy of 10million per year, with outlying areas using LHR/MAN/EMA/LTN/STN and BRS. That's a fraction of its potential thanks to the other airports.
So explain to me why CF would be so vastly different? Like I say, you have a far too simplistic 'Yorkshire pride' view on this, and you seem to be answering rather defensively against any critics, which quite frankly puts many off and I'm wondering why Ive even bothered t be frank.