I don't believe you get pneumonia from being cold. I think it has to do with bacterial infections. :clown:
I have used a drysuit and it is great at keeping you dry. Keeping warm is achieved by the clothes you wear under the drysuit.
That said, I preferred a good wetsuit, personally. Cold tolerance is very individual. I was able to go out in 25-35 deg air and 35 deg water temps with a Ripcurl F-Bomb suit, 4mm core, 3mm extremities. It actually kept my core dry most of the time. Taped seams and good neck, wrist, and ankle seals are important in wetsuits.
On top of that, I wore 3mm neoprene socks, wrestling shoes, and an old JP tour coat.
But: riding in those conditions, even with a warm suit, still sucks IMHO.
PS: I cannot stand gloves, so I never wore them. No problem with good handlebar sprayers.