Could be very cool indeed.............
A few ideas :
Outer Atolls of the Seychelles out of action at the moment due to piracy issues - a shame, it's just insane fishing
St. Brandons - the guys I know running the live aboard trips are running them as saltwater fly fishing trips
Australia - some insane top water stuff on a serious mother ship operation in the Coral Sea, have wanted to go there for ages :
http://www.nomadsportfishing.com.au/ - utter insanity, lots of videos on their site. GTs, doggies etc.
Madagascar - seems like some very good fishing, would need to be organised via one of the French companies running trips down there - GTs, doggies, snapper etc. I believe
West Africa - some serious fishing in some serious places, but not somewhere for a big group and not a place for people who have not really travelled much before - southern Angola would be the place to fish plastics for insane numbers of kob, plus garrick off the top etc, then nearer the capital Luanda for serious tarpon, monster jacks etc. Gabon for big tarpon, cubera snapper, threadfin etc. - no GTs on the west coast of Africa.
etc., etc.,
If you want to get hurt, you need to chase big GTs off the surface.