Moderator speaking here.

I think it would be a nice thing to have various Moderator/Editor Badges that indicate how long this user has been Moderator for this Channel already, Just like with the Sub Badges.

If the Badges vary from little changes in the badge itself that are provided from Twitch itself or are customizable by the Channel Owner or even if the Badge stays the same, and it just adapts to the Sub Badge that when you hover your mouse over the badge that it aside from badge indication also displays the duration next to it, like when you hover over a Sub badge.

Either way, it would just be a nice thing to have. Would be a little effort change that goes a long way, as it would add some Authority display kinda thing that you would usually "show off" with the amount of watch time you have on the Channel.