To be honest, i don't think peoples are trying to get port for their country ( exept for phil / zuzik and a few others ).. Why would peoples try to buy out a port worth millions from another country just to get 10% bonus in influence wich is kinda useless if you ask me.. 
So here a suggestion to save the day.. again ..  i think.. 
- Attacking / Defending Fleet get a 10% Bonus to chance to hit and chance to dodge. ( Of that port country of course.. )
- Damage on you're fleet would be reduced by 50% after any battle.
- You cannot lose any of you're "SHIPS" on any of you're country port.
Of course there a problems to this. Anyone can switch country at anytime.. I can already see abuse of switching before attacking other fleet to switch back after.. Etc etc.. 
SOoOo.. Personally, i would do one of those: 
- Block "Meet the governor" to counter peoples from switching country. ( People are smart enough to choice their country on the first sign-up, why change it after??)
- Lose all their ships, if they wanna switch country ( Country Treater Result ) 
- Lose 50% of their current Fame and 50% of their fleet. 
			