I like the colours more as well, not only because of the aesthetics and tradition (which is good for me too), but because or something more practical: how easy it would be to mix up gold and bronze at a glance.
I feel that 3 is useful because the senior staff does have a tendency to become more stagnated than the junior officers, and that’s to some degree unavoidable: promotions are given mostly as new posts are being created, and that happens either because their occupant leaves (and they can be back with full rank, becoming an issue), or because logistics call for a new post being created anew, such as a new ship being deployed or a department rearranged. Adding flexibility to the staff lets us work better despite this.
My main concern with a new lt rank is that, if the rank is intended to solve stagnation for full lts, lieutenants that are candidates for senior rank will be stuck there with the lieutenants that intend to remain there. The problem won’t go away, it’ll just be easier to disguise. If we accept that much, I’m all for it.
Idea 2 allows for something similar. Right now there’s no real distinction between Captain and Commander. Yes, captains are senior, but the expectations being different for each just plain don’t cut it: commanders have to perform in lieu of a captain way too often. If we divide the command rank (and for this is irrelevant if we divide Commander, Captain, or both) the seniority difference will be observed regardless, and we get a free rank we can use to free stagnation anyways.
The idea of making a lesser jump from lt to lt-cdr is probably unworkable without major changes, though. The jump is not, I think, the result of a conscious design choice but rather an artifact of senior rank being assigned on an availability basis. Senior officers are expected to be major factors in organizing the community and leading in combat, and also have access to information that it’s not always clear how much we should be revealing. To soften up the transition we would need to open some day-to-day planning to the senior lts, which gives us this problem: letting the senior candidates in makes a lot of sense. Letting the officers who desire to remain as senior lts, on the other hand, doesn’t: they already made a choice not to advance into senior rank, and we’d be throwing their way a lot of responsibilities they already rejected.