I think its to easy already - I did my last nation change start to marquess in about 12 hours without really trying hard. I have seen it done in less than an hour.  I did spent about 3 hours before that positioning ships and checking my cards to make certain I had everything I needed. The first time I ranked up in a nation, it was a small nation with no hostile targets.  My hostile targets were the top ten most infamous.  Despite a lot of warnings I attacked them.  I chose which ones and how i did it very carefully. Any target is possible to hit if you plan correctly.  Yes, I had to deal with any consequences of my actions.  Its part of the game.
edit - adding this
As for those who are the targets,  I don't think you should drop of the list because your hostility is lower. 
You could attack members of a nation, and then have your hostility removed and not have any consequences of your actions.
			
				
