Tyncale
The danger of Turncout Companies that own Holdings that are part of the core defense of a Settlement is always there, but this seems like a comparatively easy way to weasle yourself into a heavily fortified Settlement.

It makes who to put in the core 6 a meaningful choice.

Do you make all core 6 hexes solely founding company holdings to minimise the sabotage risk? Or do you instead spread your core 6 between 6 different companies so the opponents need to feud multiple companies and when the inevitable betrayal occurs it only effects a single hex ?