Hi,
"It's my first time to post in the PP forum although I've been lurking for quite sometime. It's a watch that I would get for when I hit 50."
That my point, defining a watch that would have brought you to Patek Philippe 20 or 30 years earlier!

"I'm thinking its the Nautilus line if you want to be a bit more casual."
More casual yes, but as you wrote earlier, the Nautilus is definitely a watch you need experience to appreciate IMO.
"But I suspect PP in general is not about being casual. Their watches always has that air of occassion around it."
It's to be decided!
Cheers
Dje