Most guilds approach guild ranks as if they were in the army. They set the ranks as if they were a hierarchical chain of command, where each rank commands the ones below it.
But realistically, most guilds are small enough that there's really only one power relationship: Officers and Members. Officers command members, and that's pretty much it. The actual hierachy is very flat, regardless of the number of ranks.
So rather than looking at ranks as a chain of command, it might be more productive to look at them as mutually-exclusive "tags". These would label your membership in specific ways. For example, many raiding guilds will have "Raider", "Guild Friend", and "Alt" ranks. There's no chain of command present in those ranks, though some will be higher-ranked than others. It's just a way of labelling characters to make it easy for the leadership to sort them.
So what other ways of labelling characters might there be? One example I found on Elitist Jerks (sadly, I don't remember the guild that did this) was a guild which had the "Tank", "Healer", and "DPS" ranks. Now this is very useful way of categorizing members for a raiding guild. It allows the leadership to quickly see at a glance exactly how much of each category they have online. This is especially useful with hybrids, as you could have 3 paladins online, and each in a different category.
This setup was pretty interesting before 2.3, but with the introduction of Guild Banks, it becomes downright amazing. Permissions in the Guild Bank are tied to rank, and having different ranks for each role has a lot of benefits. For example, you could dedicate a Bank Tab for each Rank. Healers would have their own Bank Tab, dedicated to healing materials. (I forsee a lot of mana potions being stored.) Tanks would have their own tab, etc. You could even split up DPS into "Melee DPS" and "Ranged DPS" and give each of those groups their own tab.
The other advantage comes with repair costs. You can set different withdrawal limits for each role/rank, and perhaps give the tanks a larger allowance to fund their repairs. There are a lot of intriguing possibilities with this setup.
The key idea here is that treating guild ranks as a power hierarchy is possibly the most limiting way to look at ranks. Approaching ranks from a different angle can allow a guild to use their Ranks and Guild Bank much more effectively.