I cannot guarantee it will be better or faster, but I think it would be. Depends on what is the alternative, which you haven't really mentioned. Or even the resource consumption of current widget engines.
The only one I've used is the desklets engine for gnome (Python) and I don't remember it's usage of cpu and ram
I would need to investigate to see if it's really interesting to do it anyway, but being interpreted JS, and python, and using qt in the case of some I would imagine its not little.