put this in a drafts action to replace yr draft with its ｆｕｌｌ－ｗｉｄｔｈ　ｅｑｕｉｖａｌｅｎｔ

full-width drafts.js

function fullWidth(input) {
    var
        dict = "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}",
        offset = 65281,
        out = "",
        n,
        letter,
        codePoints = [],
        index;

    for (n = 0; n < input.length; n++) {
        letter = input.charAt(n)

        if (letter === " ") {
            letter = 0x3000;
        } else {
            index = dict.indexOf(letter)
            if (index !== -1) {
                letter = offset + index;
            } else {
                letter = input.charCodeAt(n);
            }
        }

        codePoints.push(letter)
    }

    out = String.fromCharCode.apply(String, codePoints);

    return out
}

draft.content = fullWidth(draft.content);
commit(draft);