What is your objection to 36MP when it is clear that the added resolution has no negative effect on IQ? You gain all the ability to crop, the effective reach/pixel density, print size, details, etc. If you don't need any of that then it really doesn't matter but it doesn't cost you anything. Plus the difference between 24MP and 36MP is really not that huge in terms of storage given the price of storage these days. It is no where near the differences of the last gen when you could have 12MP or 24MP bodies and the relative cost of storage was higher.
36MP just sound crazy big because we are used to smaller number. back when camera wee 4MP the 8MP camera were ridiculed and seemingly unneeded (although back then the increased resolution came at a definite cost in reduced IQ).
I 100% agree that 24MP seems about right for a FF image. The real kicker though is I want a pixel density equal to the D7k, I want about 16-18MP minimum in the DX frame for wildlife. If I was to go for a D600 then I would be loosing resolution from my 12MP D90 to an effective 10.5MP, that will actually be a huge step backwards for much of my work.
So I must have the pixel density that gives 16Mp DX images, and this comes with the side effect of giving me 36mp FF images - I don't mind this extra resolution which is fine for landscapes and architecture, or can allow looser compositions. The 1.2x crop because an interesting setting give 24MP images avoiding the soft far corners of lenses but giving much more sensor area than standard DX cameras. You can also do interesting things like you the lossy compressed 12bit RAW in 36MP mode and get smaller files but actually more details than the 14 bit loss-less compressed you might normally shoot at to maximize IQ.
There may be complications with some of the Sony sensor because they share development teams for some stuff. Still I think Sony could offer some other technologies that are not entangled with nikon. E.g., Pentax uses Sony sensor, Panasonic and Olympus are now using Sony sensors. Sony's strategy seems to be that they are happy to sell sensors to other companies since that is easier direct profit that trying to sell more cameras. If Canon ask for 500K FF sensors and Sony makes $50-100 per sale then that a better proposition than Sony trying to steal hundreds of thousands of sales from Canon which is hard work and less likely to happen. Sony's sensor fab is very, very expensive and they need companies like Nikon to use their sensor fab facilities.