othyrsyde said:
That's sad the history or language wasn't recorded
Oh, it was recorded. But bear in mind that the records were sparse, and kept in monasteries, which are notoriously combustible when there are Vikings, Angles and history-rewriting Gaels in the vicinity.
To get the Picts to survive as a distinct kingdom, you need two things.
Firstly, King Óengus I has to defeat the Kingdom of Strathclyde. Having subdued the Gaels of Dal Riada, he went on to lose what must have been a significant battle in 750 to Strathclyde. Change the course of that battle, with Oéngus possibly establishing overlordship over Strathclyde, and you have a secure kingdom which could not only repel the resurgent Gaels, but would be externally secure enough that Óengus could crush internal dissent decisively. Óengus strikes me as the sort of character who was ruthless and determined enough to make a good job out of the kingship, much like Máel Coluim II did 250 years later.
Secondly, you need a better response to the Viking raids on Pictland's eastern seaboard. While it's difficult to ascribe them as the absolute cause of the Pictish collapse, there's no question that the raids severely weakened the Pictish kingdom and moved the centre of political gravity south. Though they never established a lasting foothold in the north-east, the Vikings did enough damage that it became easy for Cináed mac Ailpin - whoever he was - to seize power.
These PODs preserve the Pictish kingdom as a
political entity. However, there's a lot of debate among historians about just how Gaelicised the Picts had become, even prior to the mac Aiplin takeover. There's a not-inconsiderable body of evidence to suggest that Cináed was himself a Gaelicised Pict, and that he represented the fifth-last Pictish king rather than the first Scottish one.
So while you might preserve 'Pictavia', with Pictish client kingdoms in Dal Riada and Strathclyde in the short-medium term, it may well become Gaelic speaking in the long-run anyway. The church, and it seems the aristocracy, were already in close cultural communion with Ireland. What you would have, though, would be a completely different foundation myth for the lands which went on to become Scotland.