Marston died so early in WWs creation and development. I almost feel like her comics had no time to breathe in the Golden Age. Like, everything happened so fast and changed so quickly once new writers got a hand of her. If I remember correctly, Marston didn't even want anyone else writing WW besides him. What do you guys think WW would've been like if Marston had lived longer?

I fear there was a genuine chance for her to end up simply forgotten, since if Marston had continued to write for another 10-15 years, the kinkier aspects of his creation would have continued along with him. Which courted controversy, and would only increase as time went on, so when Marston did die, Wonder Woman might have become kinda toxic and in need of a hard reboot.

Though you might be right that the special arrangements between the Marston estate and DC might have been so different that there would be no Wonder Woman at all.

Hard to say. The comics code authority came in the early 50s I believe, so even if Marston had continued to write the book he would have had to adapt his style somewhat.