我觉得你对英语的理解过去形式化,问题出自这里。例如:你问能否说I don't want being a scientist. 这说明你不太明白want+doing 用法和want sb doing 的区别。want doing 这里的want = need 如: My hair wants cutting. 英语不说I want being a scientist. 要用to be. 但可以说I don't want myself being a scientist.意思有两个:一个=to be. 另一个意思是我不想(继续)当科学家了。这需要根据语境判断。
回到你的问题:I want /wanted to be a scientist, now I am. 这两个用法都对。用一般现在时表示这种你的一贯想法,=I always want to be a scientist. 用过去时,表示你过去曾有当科学家的想法,比如小的时候,现在实现了。你要知道:过去有过想法,不一定就意味着现在就没有了。现在想不想需要有语境决定。
至于动词静态还是动态,也是灵活的,有时会随语境而变。假设做游戏,你说想当科学家的角色,就可以说I'm wanting to be a scientist. (现在进行时)这里就是动态用法。外刊例句:
Many times I have wanted to do things differently.
I have wanted to take a different route.
I have wanted to have my way.