20 (item upgrading) When we find out more details about the new upgrade system next week, you will be able to effectively delete 24 (transmog) as there will finally be many more legendary choices.
Obviously no details about item upgrading are available just yet, but if they do it right and make any and all weapons and armor (excl. exotics) progressively upgradeable to max legendary, we will be able to be unique finally...effectively removing the need for transmog. Of course a straight transmog system would be the simplest solution, but where is the GRIND in that???!