Why do folk travel biz/First? Let's be honest, it's not for the catering and it's not just about the space. They pay the extra so they can work better or sleep sounder.
I wouldn't take an infant up front for fear of spoiling everyone's journey. Some folk know the risk but don't seem to give a damn. Speedbird_heavy seems to revel in it. On the other hand, loud conversations have the same effect. What to do - ban talking?
No easy answer. I'd be all for designated 'quiet zones' as some trains have but they'd be difficult to implement. Alternatively, an insulated 'noise zone' for the infants and rockstars. And to promote mutual tolerance, permit smoking in there.
For the hard of humour, I do not promote smoking in front of infants.