Absolutely this. Better on so many levels... If we must persist with private vehicles in dense urban areas.
Even the particulate pollution would be massively reduced. Think of the difference a small 14" wheel an tyre supporting a 800kg car versus a 2100kg SUV on 260mm wide, 22" tyres
It would probably be more productive for London as a whole to restrict car size / weight than charge ULEZ.
Imagine the difference if something like the Kei car class was the norm.