1. I'm very familiar with the bug tracker, I've used it on a number of occasions. Both in terms of reporting bugs, and searching for pre-existing bugs in an attempt to find a fix (or if I can add details to help find a fix).
2. At the end of the day, it's Schema's baby. I know he has very big plans for the game, and I believe he has so far been very open minded. Depending on the feature, it would range from extremely dissapointed (space whales/leviathan) to indifference. I would try to talk to the devs and find out the reason why they denied the suggestion, "Do you have anything planned that is similar, or more or less does the same thing (or the opposite, for that matter)?", "Is it just too difficult or not feasable?"
3. Personally speaking, I have been very, very keen for creatures (including my beloved space whales) since I discovered StarMade (a very long time ago). I am fully aware that developing a game takes lots of time, effort, and sometimes trial and error. You need to start with a concept, flesh out the concept, figure out how it's going to work, concept art, finalised concept.... And then you start creating assets for it, and finally you can begin putting it in the game. This process would more or less take place with every feature in the game concurrently.
3 tl;dr. Making a game takes a long time. There are certain priorities for features, and they are more or less done from scratch. I would be dissapointed if a feature I was looking forward to suddenly got scrapped, but so far Schema and the Schine team have only shown we can trust them with it. Even if it means waiting a little longer, which I'm okay with.