much more shaky peace after Hastings, with the Harrying ending in a bloody stalemate, with the Scottish king moving in pushing Margaret of Wessex's claim, initially for the northern parts of England, which aren't under Norman control
This basically can't happen long term. Scotland has far less fertile land than England, and thus can't sustain anywhere near the same population. Even if the place was twice as rich per person, it still won't achieve this.
much more shaky peace after Hastings, with the Harrying ending in a bloody stalemate, with the Scottish king moving in pushing Margaret of Wessex's claim, initially for the northern parts of England, which aren't under Norman control
Have Hastings a less complete victory. Have either Harold or one of his brothers survive the battle or else have one of his sons be less of a non-enity and force William to fight an extended campaign to consolidate his control of Wessex and the south. Have Malcolm be a bit more poltically savy and spend less time looting the north and more time winning friends and influencing people.
In this instance Malcolm Clanmore could as the husband of Margaret of Wessex more sincerely pose as the champion of her brother, Edgar's claim to the English throne and invade northern England. With William tied down in the south he could set up Edgar as a puppet ruler in Northumbria and eventually remove either Edgar or his heirs and take over northern England. Alternatively Edgar could be killed somewhere in Mercia fighting the Normans leaving his sister as a possible heir. Much would depend on the whereabouts of the sole surviving Saxon heir, the mostly forgotten Harold, son of Edward the Confessor's nephew, Earl Ralph the Timid.
In time Scottish control of the north would solidify and the extra resources acquired would make the medieval skirmishes between the two Kingdoms a bit more evenly matched.