I will be happy assisting in this good work. However, we need to define first (and for that, we have an option of chat I think) which questions we shall consider to leave with 'grammar' tag. At times it may happen that the volunteers may find it confusing whether the question is actually of 'grammar' or not. In that case, we shall chat, take others' opinion and carry on.
Cleaning up the tag 'grammar' is very important as you suggested earlier. And, as I replied then, I'm ready now as well.
I'm available on weekends (not all those two days though) but the time won't be fixed. However, 'hours' will be fixed. Say, I contribute 3-4 hours of mine. Are you or anyone available all time?
Okay, in case if no one is there to chat, I leave those questions but surely mention them in chat.
I'll edit the questions that are typically of 'word usage/meaning'. I'll keep all tense and sentence related questions as grammar. Also, there are plenty of tags and as we check, we'll take decision on the spot.
Thank you for initiating this. All the best to us!
:)