My account has been marked inactive, but I don't mind the red warning message, tbh. I think the warning itself is very self-explanatory and not hurtful. It also explains what you can do to have the inactive status reversed. Having an alert a week or so before the official warning seems redundant to me and probably won't end up increasing activity. It's really not a big deal WebFlake admins require a few posts to get your account 'unlocked'. I don't have an issue with it.
I own a small music/general entertainment forum and there are a lot of inactive members on my site. So from an admin standpoint, I would like to implement this inactivity warning (or something like it). I've tried to offer incentives to get members active (giveaways, closed club with exclusives for active members only, etc) but it doesn't seem to work as well as I hoped. My co-admins and I reached out to some members via email and they either logged in once but didn't post or people never logged back in. So I understand the struggle of having a community with inactive members.