With a POD after 1200 AD, the challenge is this: Make Scotland a Francophone country to the present day, with French as the first language of >90% of the Scottish population, and French as either the official language of the Scottish state and government or the lingua franca for the country.
Scots Gaelic (Gàidhlig) may be spoken to a greater or lesser extent than IOTL, and Scotland may be officially or de facto bilingual French and Gaelic. English may be spoken in border regions or among English immigrants, but should not constitute more than a minority language. Similarly there may be many other minority languages as IOTL (e.g. Irish, German, Spanish, Swedish, and more recent communities such as Chinese, Punjabi, etc), but these predominantly remain spoken only in the home, and are subordinate to French.
What this might mean in terms of politics and religion is up for debate. Would it butterfly away the Scottish Enlightenment? Would Scotland be Protestant or Catholic? Would there still be a Scottish monarchy? What would Scotland's relations with England be like?