For spelling, I believe that it could be done through a macro. And, I suppose the macro could be run through the command-line interface, now that I think of it. For grammar, there is no way, because for most grammar points, there are not suggestions.

I do not have the skill to write such a macro but someone else on the forum may.

The "risk" is very real. It is highly likely that Word will make a document worse rather than better without a human brain making decisions. Search the Internet for "Stupid AutoCorrect" for some idea of what can happen.