I don't think there's much call for fullwidth Latin characters for that purpose. Ordinary use means typing with whatever your input method gives you. This is generally not fullwidth characters.
A clean grid would be desirable in formal use, but formal use means trying to avoid Latin characters as much as possible. It's generally possible. Plaques and the like are much more likely to say e.g. 二〇二〇年 than to say 2020年.
Grids are not just for formal use, they're useful any time you want to have aligned text, e.g. if you want to write a markdown table mixing Latin and CJK characters.
And I doubt you'd want to eliminate all formal uses of Latin characters. E.g. a plaque about a person would likely want to use their preferred name, which might be in Latin characters.
A clean grid would be desirable in formal use, but formal use means trying to avoid Latin characters as much as possible. It's generally possible. Plaques and the like are much more likely to say e.g. 二〇二〇年 than to say 2020年.