I agree that there needs to be a system in place and this also seems to be a common problem with most games - how to handle inactive alliances.
The original Guild Wars game did this well. In that game, if a guild leader did not sign into the game for more than 30 days, then they were auto-demoted to Officer status and the most senior officer in the guild (that had been active in the last 30 days) was auto-promoted to leader. If no officers qualify then the most senior member is promoted.
I’d like to see a similar system here, and in most games.
If the leader hasn’t played in 30 days then they should be demoted to Co-Leader and the most senior Co-Leader promoted. If no Co-Leaders qualify then move to Elders then finally to members.
If no one in the Alliance has played for more than 90 days, then the Alliance should be dissolved or at the very least taken out of Alliance search results.
I think most people’s main argument against auto-demoting a leader is “What if real life issues happen?” Yes, it happens. A leader has a car accident and is laid up for awhile, or goes on a month long honeymoon to Europe or moves to a new town. That’s why we have co-leaders and they need to be given the authority to manage an Alliance appropriately in a leader’s absence.
If the absence is planned then most competent leaders will step-down and appoint a new leader until they return. This is why it’s important to have people you trust in the co-leader positions.
However, let’s face it. Most people that haven’t signed in within 30 days have totally abandoned the game and they aren’t coming back. Those that have unforeseen real-life difficulties likely have more important issues on their mind than an alliance in a mobile game and would probably be glad to know things were taken care of in that game he enjoyed before X happened.