I'm with dawnstar on the killing players off bit. If characters lag behind and start going off the mark, not going anywhere or just simply vanish, disappear for weeks or whatever and just all of a sudden posts something relating to an old irrelevant time in the rp.
Or they do a real stupid action like attacking a big feelt of marines or attacking a base or a crew of pirates by themselves, something like that.

I think dawn island is good for a next island spot.

As for question 3, something involving the marines. Like how luffy and zoro are always getting chased down by smoker and tashigi, always having someone on their tail not making it easy for them. And maybe a mortal enemy like black beard or just an annoyingly persistent one like buggy the clown to go after them. xD