UK Start withdrawal from the EU
UK an independent country with a unique UK/EU trading/cooperation treaty
UK trading widely with the whole world and the EU
UK/EU treaty globally accepted as a model of international cooperation.
Other EU members choose to leave the EU and adopt the UK/EU treaty.
Other non-EU members adopt the UK/EU treaty relationship.
EU has ceased to exist, former members and other countries from around the world are soverign but trading/cooperating with each other under models of the original UK/EU treaties.