It's not just about the track gauge, though, but also about the other standards: flange ways, flanges, etc.
Which standard would you adopt?
When the LMS shipped out a couple of Jocko 0-6-0Ts to the NCC, they reversed the wheel centres in the tyres, and were able to reuse the axles, resulting in a flat-faced look to the wheel, but a low-cost conversion. P4 modellers could do this for 21mm gauge, but I am not sure if it would be similarly possible with other standards.
It would be easier to take model in 3mm with standard 00 wheels, and produce track to 15.75mm gauge as there is a lot of slop. Any such models would run just as well on 00 track for people who didn't want to build their own, but the splashers would be in the right place! There would be interchangeability for those who wanted to run other stuff, plus a reasonable amount of support available from existing trade sources via the 3mm scale people, especially where BR designs are being used, such as the 12T vans in the 1950s. Plus N gauge would be spot on for 3' gauge.
The short answer to the survey is no, but only because I don't model in 4mm scale!