On the 701s I think it can be split into three parts. Firstly there appears to have been a fundamental cock up by Bombardier/First on the cab layout, the exact details aren't public, but a large modification has had to be made to the 701s and other short/gangway nosed Aventras. Second Bombardier's poor quality design/build i.e. where they have fitted mismatched, too bright indicators and switches to the cab desks. Thirdly union acceptance, this seems to be quite an obstacle, although there are probably genuine concerns, see first two points, it would be naïve not to see that the introduction of new stock is an opportunity to the union for 'negotiation' whether that to progress existing pay, terms eg OBS, or wider political (more RMT than ASLEF) issues.