The Nautilus 5711, 5712 and 5726 (usually in gold) already exist or existed with a leather strap.
Here is a picture posted by our friend Miranda a long time ago (you can use our search function to find some more).
He talked about it here:
www.watchprosite.com

Credit: Miranda on PuristSPro
You also had the unique 5712 in Titanium for the 2007 Only Watch auction:
I saw one (I don't remember if it was a 5711 or 5712) on the wrist of a gentleman at a Patek presentation in Paris. He was in a very nice grey suit and the watch was just perfect. For a more "business" attire or a little more elegant wearing, the leather strap is a great choice imho.
I like Nato straps (even if I don't have any). I don't think it could be easily adapted to the case (it is not a standard "pump" stem display).
I don't know if you can adapt a leather strap on a bracelet model but it would be interesting to know
Good idea Chimaera.
Best, Mark