Please allow us to do this. For those of us that run lots of alts and/or level up crafting on multiple characters, this is a much needed efficiency. Yes, it's shared bank space but, that requires the characters to be in town where banks are at.
By not doing this what will result is people in guilds wasting time of going through the process where person A receives mail from person B only to turn around and forward it back to person B.
It's only slightly better than what "drop muling" was back in the days of early MMOs like Asheron's Call 2.