Mod capabilites / interfaces
In my opinion the upcoming C&C should have a really solid mod environment. Objects and their behaviors should be accessible and maybe even with an interface to implement completely new behaviors via lua or even c++ (or c# if you would like to support that ^^). There should be more room to create new interactions with objects. TW had a good lua system but it was lacking some very important parts like getting more information about other objects, targets, etc.
For example if you could get the target for a move order anyone could write a small lua code to recreate a chrono legionnaire, or getting the position of an object so you could interact with it.
Also an interface for new post effect shaders would be nice. It was often daunting to abuse/change the TW ones to get the desired effect.
But please don't make a tool like Blizzard that you have to use to change values. The ini/xml files in previous SAGE games were great. The only problem was they were somewhat restricting as you couldn't create new behaviors.
Oh and please don't use parts of software you can't give the community tools/information how to mod them, like the AptUI in previous games. There is a UI editor for that being made but it is also over 5 years since its first occurrence in BfME.
A happy mod community if done right ^^
Could be hard to learn for beginners if it's done with more real code instead of ini/xml.