automation the BOAT tycoon (not a mod stand alone game)
suggested features:
chose between sizes of boat ie: ship, yacht and river/lake boat (maybe jetski maybe)
different propulsion methods ie: water jet, skimmer propeller (a propeller that is half in half out the water), paddles, outboard motor and a normal propeller
ratios ie: size and degree of propeller blades how blades etc.
hull designer (self explanatory)
and so forth
I'm sure that after people get behind it more suggestions would come but this is half baked idea of mine

after you have finished this automation of course