1. Should only admirals be able to accept "demotion" to a lower rank if they decide they prefer the kind of gameplay at that level? What other things (prestige? items? nothing?) should they have to give up besides their rank if they decide to change their minds about accepting promotion to their current rank?
2. Bearing in mind that "demotion" is a bunch of other code that would have to be written (and tested to eliminate exploits), what about the idea of showing players what gameplay at the next higher rank is like and then saying clearly, "if you accept promotion, you can't go back, so be sure this is really what you want"? All things (not just player fun) considered, is this approach better than allowing self-inflicted demotions?
3. The idea that players could be demoted from Admiral without their consent would need a lot more consideration. Under what conditions could/should this happen? In other words, what's the more specific definition of "not performing well?" Is there a good metric for strategic success, or should being a good admiral include other things? Should demotion be carried out automatically (the game itself demotes you) or should other admirals be allowed to demote one of their own? What rules should exist to allow this without making it griefable or turning the Admiralty into a gang that no one who's not the "right" kind of person would be allowed to join?
Lots of opportunities for further discussion here.