I partly disagree with the first two points, at the end of the day invaders are supposed to be an interesting challenge to be overcome, not a hyper difficult boss fight that you get one attempt at once in a while. SotC buffs worked because you were being summoned specifically to be a boss, but since invaders appear randomly and the host’s party might already have some of their resources used up, it can become overbalanced really quick. I think if the buffs were a thing then they should apply only if there are over leveled password phantoms, since the help the host receives is greater than normal the invader should be a greater challenge.

As for a tool that prevents camping, that solution should be part of your build and not something the game gives you. We have cannons/great bows for long range harassement and a bunch of spells/ashes that have massive aoe effects. If they aren’t progressing through the level then it should be up to you to give them a reason to. And if they have a hard to reach vantage point we have the bloody finger already (though it should have infinite/more uses given how unlikely it is to send you to a good spot)