Description:
I really like how the "avatar", from the C&C3, works and how games like AoE upgrade in eras, this really gives you the idea of evolution in the gameplay. With this concept i realise that the RTS genre have a lack sensation of evolution and freedom when you playing whatever RTS game.
My idea is to put many choices in the middle of the gameplay, that will change how your units and buildings works, like choose between a machinegun for your vehicle or a laserbeam. Thats change how your unit and building respond in the middle of the battlefield.
If we have same units like the avatar, who catch other unit or a destroyed one to compose his own power, the feel of freedom is more close to the gamer. Some things like eras or big evolutions changes is good in the middle of the game, because this force the player in do some upgrades or even act differently in the game.
For me, the upgrades need to be noticed when you looking to the units, like a different armor or a gun. Give a gamer the choice to give your soldiers a machinegun or a shotgun, that after the choise, is something irreversible in the game time.

Positive aspects:
Is more rewarding for the player give him a free choice of what do and what upgrade tree choose, with unique forms of play and big changes in the game time.
matches will be more competitive and dynamic in the game.

Negative aspects:
Is more hard to do the concepts of the game and artwork in the units and buildings.
It's more difficult to balance a game that have many trees of upgrade and changes in the game.

Conclusions:
The RTS genre game need to be simple to play and fast, also need to be balanced and challenging for the newbies and pro gamers, to be more like an e-sport, because the RTS is going to this way. Most people dont play RTS games because they not have patience to learn how the game works. If the game is more intuitive for the new gamers, the game became more accessible and popular, but not have to destroy the feel of challenging in the game with easy mechanics, just make the mechanics more easily understandable.