I think the main problem here is the misconception that the total playing time is the sole factor when deciding who gets to be a mod or an admin. That is very far from the truth and is also illogical in itself.
Firstly, the total playing time is not even the only factor determining a player's activity in the server. For example, a player could have 1000+ hours of playing time and be inactive for a month or two prior to mod elections. That player cannot be considered an active player at the time of the mod elections and it's therefore highly unlikely that he will be picked.
Also, staff members are not picked based on one single factor, because that would lead to many wrong decisions. Imagine only looking at a player's activity and not considering their behavior or ban history. Or promoting a player who displays good behavior, but can hardly produce a coherent sentence in English. It's always a balance of these variables, never any single one.
Finally, minimizing the game is practical for staff members as it does not require constant rejoining every time there's a cheater in the server. Seeing as all staff members connect via IRC and most have nick-alert activated, a much quicker response is guaranteed from the staff member you're calling out/nickalerting if they're at their computer and already in the game. As for regulars, the only way they can "farm hours" is by simply staying idle without pausing, and they have the full right to do that.
With that in mind, I don't think implementing this would be a good idea. It would only serve to further the aforementioned misconception about one tiny part of your statistics deciding whether you become a mod or an admin.
