Interesting thought experiment/prediction. My initial reaction was that VR seems a bit too tech intensive and niche, but you make a good point about it not needing to have high specs at all - Nintendo has often had great success with generation old specs, so why not do the same with VR? And if anyone's going to get the mainstream to go crazy for VR it'd be Nintendo.
I wonder if Nintendo in a way was testing the waters with VR/MR - in the form of Labo and Mario Kart - with a view to its next home console. But all of those games sold poorly - the first Labo only shipped 1.42 million last we know, the others didn't even hit 1 million, and Mario Kart: Home Circuit didn't fare much better at 1.58 million, despite having the Mario Kart name attached at a time when the franchise had never been more popular. Those results might lead one to the conclusion that it's too risky and more likely to lead to WiiU-style sales than anything else... or another conclusion could be that for VR to work it needs to be the almost sole focus of the console and especially its PR from day one.