"Promotion/Demotion" (roles) bot

So, I've been working on a server for a faction on a game, and there's multiple (faction) ranks. And I want Officers (highest faction role) to be able to promote/demote others, however, I don't want to give them access to roles to do it manually, since they're not even moderators and not even moderators have permission to mess with roles. Is there any bot that can do this through a simple command? Or one that I can use to make a simple command such as "!promote <user>" / "!demote <user>"? (Yes, I have looked, and I didn't find any, and if I have found one, there's a high chance it slipped right by my eyes.) The command would work like this: "!promote <user>" would check the current rank of <user>, remove that rank and give them the next (higher) rank. "!demote <user>" would check the current rank of <user>, remove that rank and give them the previous (lower) rank, so no need to ping a whole role or anything like that.