"Player X has logged on" announcements: The MMO I played before COH came back had an announcements channel for the various social groups, so that you would know when a friend or a guild member had logged on without having to keep constant watch on the guild or friends windows. I kind of miss that here in COH. A lot of times, I'll have the supergroup and global friends windows closed down and don't realize there are members that have logged on until it's too late to matter. Code these "login announcements" as a separate channel and people who don't want to see them can just remove them from their chat window.
Audible tone for more than just /tell messages: It would be nice if the supergroup, coalition and friends channels had an audible ping, similar to /t messages. Because the color of supergroup chat is so similar to LFG, pet and NPC chat, those messages frequently scroll up and away without me noticing them. I tried putting them in their own window, but if I'm in a team and concentrating on combat rather than chat, it can be a while before I notice that someone has posted. It would probably also be a good idea to make that audible ping optional, so that if the chat was super active, they could disable the audio at will.
Option to display time stamps on chat messages: If this option exists, I sure don't know how to find it. It's kind of annoying to be afk for a while and have no idea how long ago someone posted an opening for a team in LFG or how long I've been accidentally ignoring someone who said "Hi" in supergroup chat.
Ability to see which coalition members are online: Again, if this option exists, I don't know how to access it. Right now, the only way I can tell any of our coalition members are online is if I've global friended them, and if I've done that, what's the point of entering into coalition. . .
Option to change chat channel colors and save those preferences: Some of the colors are so similar that they are virtually impossible to tell apart, especially if chat is scrolling quickly. Local and League chat. LFG and Supergroup. Right now I have to keep them in separate windows so I don't get confused, which means I end up spending a lot of time customizing my chat tabs for each alt. If we could customize the chat channel colors and save those preferences to the preferences file, that would be a nice quality of life improvement IMO.
If any of this stuff already exists, feel free to educate me on how to achieve it. I'm sure there are a crapload of slash commands out there that I'm not aware of.