Honestly, I feel like Ideas 2, 5, 6 & 7 are all easily doable, and things that Arthur should be willing to do. Though 6 & 7 both lack something that would actually make Wiglaf come to stop them.

3 seems outside of the realm of possibility for them, as they don’t have a Mad Scientist to work out how to build the Weather Manipulator, and it doesn’t include how to weaponize it. Even if it’s something easily weaponizable, as forming Hurricanes, Tornados, Floods and Droughts by messing with the weather would be easier than not doing so.

4 Seems to be a bit of a challenge for them at the moment, particularly without Arthur’s Dragons, but is potentially doable. Though it would likely involve killing soldiers, so it might be off the table.

1 just involves murder, but is indirect enough that Arthur might be willing to do it… if he still had his dragons to light the fires for him.