Account Bound mounts means mounts don't take up an item slot, how much more free bag space do you want? at some point you need to ask yourself what the point of even having bag space much less bigger bags is. just leave it.
If you are aoeing mobs as a frost mage your down time to just drink and get mana back coupled with long mob respawn times means you'll save 0 actual time mass looting, the difference will be so small that its just not needed.
Hell, I'm not even sure you will get me to agree on something like guild banks, because if you're not trusting your gm/officers muling items on alts not to jack your guilds shit then that's not vanilla.