I'm British, so I have a bit of a Britain-centric view...
I'd rather have it start at the fall of the roman empire or something. I'd want to cause/stop the christian schism, or see/cause/stop the rise of Islam, or take advantage of a collapsing Roman Empire, be(come) King Arthur, or maintain the Roman Empire in different regions as pocket empires or utterly wipe it from Europe entirely!
In Britain I'd want to see druidism or people fend off the Angles and Saxons, or further spread Christianity.
There was a major climactic change during the end of the Roman Empire which caused migration of people, so that would be an interesting challenge and scenario too.
I'd rather have it start at the fall of the roman empire or something. I'd want to cause/stop the christian schism, or see/cause/stop the rise of Islam, or take advantage of a collapsing Roman Empire, be(come) King Arthur, or maintain the Roman Empire in different regions as pocket empires or utterly wipe it from Europe entirely!
In Britain I'd want to see druidism or people fend off the Angles and Saxons, or further spread Christianity.
There was a major climactic change during the end of the Roman Empire which caused migration of people, so that would be an interesting challenge and scenario too.