*Cash on Delivery Mailing system.
Just make it so that items cannot be accepted unless paid for first at the senders request. Also add an option to reject mail and return items to sender.

*Inbox/Outbox for Mail.
This would go along well with a Cash on Delivery Mailing system. Make it so that there is an Outbox for mail that has not yet been received, with the option for the sender to recall it. Would solve any issues with typos on your friends/clients names via mailing user errors.

*Drag menu, Option to "Send Mail to User".
This would allow you to instantly fill in the username requirement when composing new mailing messages to your contacts or users in your line of sight. This would nearly eliminate user errors when sending mail containing attachments.

*Dungeon Completion Screen Alternate Options.
A series of options upon completing a dungeon would be a nice additional feature, in addition to items gained, a conveniently placed "To Bazaar", "To Arcade", "To Haven", and "To Guild Hall" in the completion screen that instantly take you to the said areas would be very useful.

*/B T chat command.
"/B T Message" would send a private message to every contact on your buddy list at the same time. An excellent addition for party advertisement on massive friend lists, as well as private trading.

*Additional Weapon Hotkey in Controls.
While the game already has Previous weapon and Next weapon hotkeys for cycling, if you're using 4 weapons at once via premium feature, this can be annoying. I suggest adding a "Switch to Weapon 1", "Switch to Weapon 2", "Switch to Weapon 3", "Switch to Weapon 4" Hot key Feature for those that would like to utilize it.

*Additional Game Optimization.
Many areas run too slowly and have issues for a lot of users. Especially Firestorm Citadel. I would like to suggest that there be additional graphics optimization options added to the game. Such as "Disable Weather", "Reduce Fire effects", "Disable Glow", and "Simplify/Eliminate Bottom Layer View."

Thank you for the wonderful game, I look forward to the future of it's development. I hope someone internally reads and considers my suggestions. :)