IMHO, the "big modern three" - Spectre, Empress and Eureka - are compatible not only in proportions, but in operational accuracy as well. LOTS of new companies that claim to specialize in "modern" figures don't know anything about gun handling and movement anatomy!
I also like very much the Somali pirates from Forlorn Hope, they have a lot of character and can also be used as Indonesian pirates with minimum conversion (I will only add bandanas, cloth masks and parangs to mine).