You should consider the Maldives. Due to the dispersed nature of the dive spots, its best to do a live on board Safari Cruise to get to the various atolls. Most safari boats are well equipped and very comfortable. Its usually a one week or two week deal and normally they visit the central atolls of North/south Male (MAR-LAY) , North/South Ari, Rashdoo and Felidhoo. The best time would be Nov - March, although Oct and April would be fine too.
Pelagics:
Whale Shark (almost a given if going during the above dates)
Hammerhead (Only saw on two out of three trips there)
Mantas (almost a given if going during the above dates)
Gray reef sharks (almost a given if going during the above dates)
Also there are the rare safety stop dolphins, sailfish and wahoo.
If you travel far south to the equator (via a domestic flight), you can see Tigers and Oceanic White Tips. Thats usually a 2 week deal though and i personally havent done it myself. So caveat emptor.
I lived/dived off a boat called the southern cross. They have dedicated tables for camera equipment, on-suite toilets, air conditioning and even a small pool on the upper deck. The diving is done from a auxiliary boat called a Dhoni. It holds all the dive equip and the compressor ...etc. So at night (and during your afternoon naps) you dont hear the compressors. it was all very comfortable. let me know if you want more details.
Eudon