Tears of the Moon
The use of visible ducting was and is championed by British architect's Sir Richard Rogers and Sir Norman Foster these being the best known. Hidden ducting increase's costs on both build and maintenance so is now often value engineered out, and you will find it used at the airports in HK/SIN/Doha/ Muscat/ DXB and many others. I worked on those named so I can tell you its there, and a few others as well.
The design ideally would reflect something of the character of the area (or it would do if we were sitting on huge oil / gas reserves, or were a commercial hub for a large section of the Far East). Instead we are a small island which is possibly going to have to wake up to the fact very soon, and Manchester is a secondary gateway within that, therefore we end up with a "shed" much like the other sheds / distribution centres / shopping centres scattered around UK Plc, very few of which have architectural merit, but serve a purpose.
I would very much like to be involved in an architectural statement building, but there really is not the money for it, and as everyone knows shopping is where the money is for an airport along with the car park. As long as the premium lounges are catered for as you say, most people do not seem to care about the airport surroundings, it is all about foot fall. Sad but true.
Regard's
Mr Mac