there are no current way to do this in NW.Js nor chrome AFAIK (well you can use a chrome or nw.js argument to disable v sync but then the game will run as fast as possible as opposed to a fixed framerate), the dt minimum value can be fixed to fit a 60 fps display so if the game goes under 60 fps, well, it will get slowed down.
using dt is still important to ensure that the result will act the same regardless of the framerate (so a 144Hz display or a 60 Hz one will still be calculated the same).
But apart from performance reasons (executing the logic and rendering at a fixed 30 fps is not as costly), if it is done well, dt ensures that as long as there is no lag or freezes, the game acts correctly and is as fluid as it can (since the movements aren't framerate dependant but time dependant).
Also I never thought of a single case when anyone would want to use every X seconds with such a low value as 1/60, like why even do this? I don't get it, if your dt implementation is correct you simply don't need nor want that, perhaps I'm missing something (it's early here).
I still agree however that a fixed framerate would make development easier for some people working with devices with a low perfs/framerate ratio, or simply make development faster as there is no dt to use (even though dt isn't that hard to use once you understand it, but as said for deterministic resuts while still being the same speed on all system is a must it's important), however input based replay would indeed work nicely, instead of what we can do currently (basically a time based replay which is not as easy to do!).
EDIT: After reading it again it feels like this post is agaisnt fixed framerates, it is not, I want to see a fixed framerate as an option, screen tearing is a light tradeoff for all the advantages it gives, this post was simply trying to explain how to compensate from the lack of it currently. Oh btw GM:Studio allows a fixed framerate but unsure if they do it the right way.