One factor that differentiates top players from the rest is APM (although it is not the most important one, it makes a significant difference). Ideally winning in a RTS would be as much related as decision making and strategy as possible.
A feature that might help low APM players would be the ability to schedule an action, even conditionally. Examples (AOE 2 based):
- Build another lumberjack in a better position in 5 minutes;
- Build a mini-wall to protect miners IF any enemy unit is visible on the villager sight of view;
- Build a tower once feudal age research is finished in a determined position;
- Build a second town center once castle age research is finished in a determined position.
This could be expanded for army control / reactions too. To have those programmatically actions helping might able more players - those who think well about the game and predict things pretty sharply - to be high level even though they do not have awesome reaction skills.