Here is one idea, probably too late to implement but I want to put it out there none the less. A winter season. Spring, summer, autumn don't matter but winter does. Traditionally winters were when armies went into winter quarters and active campaigning was put on hold. For this, it could be a time when leaving your own territory with units results in massive attrition damage, or some other mechanism to make you keep your units in your territory. The point of this would be to make 3/4 of the game normal and 1/4 a "breather" for work on the economy or building, thus giving players who are behind a chance to catch up or players who are ahead a chance to distance themselves and prepare for spring warfare. The art requirements would be low, maybe just add a grey to everything during winter? I think this would add a new element that RTS games really haven't had and it would make gameplay more interesting, e.g. "can I finish my attack before winter comes?" or "can I hold on until winter comes?" Very dramatic!