I'll also use this place as my own suggestions thread, Ive already made a topic so why not?
Spectators eye
This can/may be a multi functional feature, sometimes, people dont want spectators in there game, like when your hosting a 16 player game the last thing you need is 5 specs lagging it up. Another thing, 4+1/6 isnt a very descriptive fraction, the + part may confuse soem noobs, they don't know it means specs yet. My suggestion is this, make another column in the lobby,in that column beside each game, place an image of an eye. If specs are allowed in the game (make it an option in hosting), the eye should be regular. If they arent, make the eye red or crossed out. When/if they allow specs, the number of spectators currently participating in the game should be shown above the eye. Would be a nice and original feature IMO.
Popup RGB color selector
Plain red and blue and ect is so boring

Primary and Secondary colors (and teritary?)
Pretty self explanitory, instead of 1 color for a team how about 2 colors? (primary would show up on minimap). And possibly teritary colors too? Units would have to be supportive of them of course but it may work eventually if the unit makers and scripters work together.
Mute button
Ack, this is greatly needed. Some noob comes on the cilent and decides to start spamming up the place, but there are no mods on. So you can simply right click the player and select mute (or somthing) and voila, no more stupid noob.

Helicopters
Would be a very intresting unit. Sorta like a gunship, yet not. If this would be made capable then that would be cool.
Fire at trees
I notice that when you command a unit it is not possible/ extrmely hard to fire at a tree or an ally unit, this should be changed.
More players
Some people have really nice connections I notcice, so the player limit shoudl be changed from a max of 10 players, to like 20 or somthing, if no one ever makes there max that high thats fine. At least they have the option to.
Underground (caves, tunnels, bridges, ect)
If spring could have capability for 3D heightmaps, then maps could have tunnels and bridges and other really cool things like that,
More later as soon as I think of them :) .