Inquiring minds want to know, what will the British flag look like if the Scots scoot? Well, it will look like this:
The reason involves one of the most famous creative heraldic hacks in history. If you look at paintings of British battles and ships before 1808, you will see that the Union Jack had only a white X, not a red one. More precisely, Azure, the Cross Saltire of St Andrew Argent [the Scottish cross] surmounted by the Cross of St George Gules, fimbriated of the second. This means, “on a blue field, a white X behind a red cross, the latter edged with white”. The white border on the red cross is required by the rule that metals (white/silver and yellow/gold) may not touch each other, nor may colors (red, blue, purple, orange, black, green). Most baseball caps obey this rule, but incomprehensibly, the Mets and Giants take the field with non-compliant caps, an enduring scandal.
Upon the Act of Union with Ireland, it was necessary to add St. Patrick’s cross, a red saltire. If this were centered, St. Andrew’s cross would disappear, becoming a mere fimbriation of the Irish saltire. Placing the latter off-center as though slightly rotated, making St. Andrew’s cross an element in its own right, (given that the implied mess at the center crossing is hidden by the English cross), was a stroke of near genius and to my knowledge completely original in heraldic gimmickry.
If the white cross is removed, all that is necessary is to recenter the red saltire of (Northern) Ireland in its obligatory white border, hence the figure above: Azure, the Cross Saltire of St Patrick Gules, fimbriated Argent, surmounted by the Cross of St George Gules, fimbriated of the third.