I actually thought a while about the objective issue. Its why I chose 3 objectives. I did the math, and turns out you can always place 3 objectives 9" apart within a 24" diameter circle. No matter how you place the first 2, there will always be room for the third.
For the ocean world rule, I wanted to make something that required players to think differently about how they created their lists. I made sure every army had ways of dealing with it. Its why I chose what i did for the exceptions to that rule. Even the daemons, for example, which have no vehicles, have plenty of flying unit options, and the other half of their list they can ambush into the center. Since everyone is getting pushed into the center anyway, they dont need to travel as far as normal. In fact, units with fast can still charge through water when they ambush.