There needs to be an option to vote out a leader. Our leader is too casual, misses war and titan flags, and we’re losing members because of it. As of now, there is no way, even for Co-leaders, to get them out.
This seems like it should’ve been implemented from the start so alliances don’t stagnate.
This sounds like you should get your alliance to shift to creating a new one without the leader:
That would be ideal, however, we got a group of great, new, high level members who aren’t looking for drama. So we’re trying to keep stability within the alliance and would like the ability to remove 1 leader, as opposed to uprooting 28.
Sounds like by trying to stage a “coo” you already have some drama 
I agree that it might be nice to have a “remove leader” option but that could definitly create more dramas… for example a hostile leadership spill etc…
As I said, the link above is a great place to start w.r.t moving on from a lost/ inactive leader.
Another thread which is similar to what you are requesting:
And a discussion thread:
Being the leader paid to make the alliance has the upper hand. People be asking for the gems back if they booted from the alliance they created. Be a headache for sgg.
Basically start a new one that guvnor suggested. If everyone is that pissed off they will join. Just think of a name for your new alliance post it in chat before you leave if the others follow them all set to go! 
She didn’t pay to make the alliance, she inherited it because nobody else wanted to be leader, lol.
However, a bunch of us co-leaders have been conversing on Line app so there’s no in-game drama to the new players.
There at least should be an option to vote leaders off if they didn’t pay the gems to make it. There are many alliances with this problem.
It’s probably never going to happen
But keep asking new players that want to stay to get line app that you are doing. Be easier to get on board to you filling up the new alliance Good luck
Although in the short term, starting a new alliance has its headaches too, like starting again from 1* titans. And, with the current PoV titan quest though you’ll find it hard to complete, starting a new alliance.
In my honest opinion, I don’t think this idea should be implemented. In the main the majority of alliances are created (and paid for by the leader). So I assume they have some form of legal ownership to that alliance. And if you give people this type of option, surely this would just become a viscous circle. It also leaves the door wide open for abuse. The best thing to do would be to create your own alliance and ask people to join you.
Good luck