Went through Manchester a few times the past couple of years, and....
Difficult to have a World Class airport when you have to cater for First Class pax flying to Asia, and Eastern European fruit pickers nipping back home for the weekend, all rubbing shoulders from check-in to boarding....
Just doesn't happen like that in most major European airports like AMS, CDG, FRA, etc....
And this comparison with the mega airports in the Middle East and Far East is pointless - all a question of money, I'm afraid, as these are nearly all state funded and designed to visually impress.....
Maybe too simple to be possible, and can't understand why it hasn't already been done if it is possible, but if Manchester wants to or needs to attract everyone from Northern England and every airline from every continent, why not let those who pay the extra for their tickets benefit from any capital spend, and those that want to travel as cheaply as possible have the poorer facilities ??
Ryanair and other LoCos in one terminal, Easyjet and holiday charters in another terminal, and regionals and legacies with their business pax in the other terminal ?? Then invest in upgrading and maintaining the facilities for the business traffic in this third terminal for the benefit of the business pax who usually pay the higher fares and expect a bit more....
Seems to work at Marseille, where mp2 is basically just a very sparsely converted and equipped hangar for the LoCos with the main terminal reserved for non-LoCos....And, of course, with T3 at CDG which, frankly, is much, much worse than all the terminals at Manchester !!