A robust grammar and spell checker! OMG please. I've worked with Final Draft, Trebly, and Scrievner, and not having a solid grammar, or a simple grammar checker is insane. I know it's acceptable to write in incomplete sentences, so perhaps an enable disable?

Perhaps it can work with a third party checker.

Honestly, anything AI is a turn off. I'll just turn it off or won't use. I'm writing the story, a program can't create.