The obvious big miss was the Pininfarina Aeorodynamica models for the 1800, 1100/1300 & mini, as detailed on the excellent ARonline website
https://www.aronline.co.uk/facts-and-figures/carrozzeria-designs/carrozzeria-designs-pininfarina-1800/...
With the models you mention, it's already too late as they came in under BL!
A much earlier Scenario would be needed where Austin and Morris really merged rather than competed, with thorough rationalisation of production and sales networks.