I have some ideas (i think somes can be done easily by a regular of the game development) I'm sorry for my bad english, if you need a better explanation of an idea, just request me!
-Add an option to show FPS in game.
-Add an option to show a timer of the game duration in game.
-Add a feature to create a groupe of units (exemple: when one is selected, the group is selected, and all in the group does the same task). That'll make less lag i think.
-For multi: If connection/computer... crash; add the possibility to join back the game you were disconnected.
For modding, i'm really into it, but it's a bit hard cause of the old tutorials, (with german screenshot - sorry if it's not german). If someone want to update it
Think about his page in particular https://trac.wildfiregames.com/wiki/CreatingNewUnits