Rejoin the EU, single market, customs union, drop sterling and take the Euro. This would almost certainly start a civil war in the UK (I am not being dramatic) but its what is needed.
EEA like Norway would be both a significant improvement, and does not require Euro. I do think we have to get to the point where we can say that actually Schengen was good and we should have been part of it before we get economically overtaken by Poland.
Brexit was -8% GDP, according to Bank of England.