If a Free Company Leader could lock ranks so no one can be promoted to them, it would fix this because the FC leader can lock the ranks that have bank access or access to the high value company chest page, and it won't matter whether or not you can promote above your rank since the ranks with the access are locked.

SE's rank system is free form, the numerical order doesn't really mean much since you can assign rights to any rank. However if your FC has a master, and two officer ranks, and several member ranks. It would be good to be able to lock down the officer ranks since the only person that should be promoting people to those is the company master. Also, don't allow any rank but company master to define the hierarchy or access rights (that's something that the company master themself can do).