You got a nice list going but here are a few things that would really make this game cool.
IDEAS:
-a possible sandbox mode made just to build and ability to fly
-armor or gear such as scuba tank and scuba suit for going to bottom of ocean
-more blocks such as bed (for sleeping and maybe saves game), spikes (to deter sharks), couches (just for decoration), fences (to prevent falling off the raft while at the same time not interfering with your peripheral vision), ceilings (to top it all off), doors (do I need to explain?) and ladders (for different means of climbing)
to add on to your "more tools" idea,
-shovel for digging at bottom of ocean for sand, used for glass?
-bow for shooting sharks at distance
-possible workbench or building grid for making bigger/ more useful things
-gun or flare gun of some sort
Stone should be an item in the game for making things such as stone foundations that can't be broken by sharks
another cool concept should be a sort of shark bait because shark meat is a great food source in the game
It would also be cool if the developers added a feature that auto joins walls to form 1 big wall that has no gapsThere's a great future ahead for this game. Even in the early stages, I find myself not being able to stop playing. Raft Developers, keep up the good work!