Ptfff, how to fix this problem? Here is a solution :
Remove ingot cost for SS mission convoy.
Change plunder so only top 20 can do it or even top 10 is ok.
To people who gonna say why top 20 get more reward than everyone else? Well, because there is reason for them to be top 20 maybe? They're better than you, they're richer than you, they're spending more time and effort into the game than you, etc...