Nothing better reveals the depth of the psychological change to modern Britain (sorry – the British and Scottish Isles) if Scotland secedes than the bizarre and shocking thought that we would have to change one of the world's most pop-iconic flags.

These designs have been released by the Flag Institute to start a debate on how this heraldic totem of national identity might be reinvented. A Welsh dragon and an English cross? A starburst postmodern union jack? A funky tricolour? None of these designs look very reassuring when you set them alongside the pride and sentiment the union jack symbolises.

Flag Institute's designs. Photograph: Flag Institute

Britain's flag as it looks now, with its merging of English and Scottish crosses, was adopted in 1801 in time for the Battles of Trafalgar and Waterloo that gave Britain unquestioned world overlordship for the next 100 years. Yet this date is misleading, as is the myth that the name "union jack" only applies at sea – the Flag Institute says it is correct on sea and land. The union jack evolved from a design commissioned by James VI of Scotland when he became James I of England and many paintings from the 18th century show our flag looking recognisably similar to that of today.

The good old flag flies big and bold in about 1700 in a painting by Willem van der Velde of British and Dutch ships pounding each other with all guns blasting. It is kept proudly aloft in John Singleton Copley's painting The Death of Major Peirson, 6 January 1781, as heroic redcoats defend Jersey from the pesky French.

Perhaps more awkwardly for the current debate, William Hogarth's painting The March to Finchley, 1749, depicts the flag being carried by soldiers on their way to defend London from Bonnie Prince Charlie.

The flag of Britain in its earlier incarnation, as well as the design adopted in 1801, has therefore been part of every famous battle and victory parade that marked the rise of an archipelago off the coast of Europe to global power – and also our descent in the 20th century. Does that make it a hated imperial symbol to be gladly got rid of? People just don't seem to see it that way. In modern times the union jack has clad the Spice Girls and been recreated as a giant Olympic spin painting by Damien Hirst. It's really quite popular. While Jasper Johns did his best to make the American flag into pop art, the truth is that British pop culture is uniquely bound up with our breezy banner.

And why not? In the time the union jack was their symbol, the British did more than build, rule and give up an empire. They were not the world's worst baddies, and in some ways not baddies at all. They became a democracy without the bloodshed it cost in most other countries. They established a welfare state. They stole rock and pop from America and sold it back and ... Oh, it's all getting a bit David Bowie. So look, how about making the dragon a bit bigger? You need to keep the Welsh happy now.

• This article was corrected to say James VI, not James IV, became James I of England.