While it sounds like it should be amazingly often, what I find is that when I'm building an economy, I want to build an economy, not have it destroyed... to make it managable it has to be continually abstracted.  So you end up with Rise of Nations, or Sins of a Solar Empire instead.
Right now my favorite RTS is Company of Heroes, because it does away with all the peasant-gathering and a simple upgrade to your builder unit makes it a fighting force capable of flanking and quickly destroying enemy units, while still having the ability to build, lay mines, etc.  So you have a full fighting force out there.  It's based on a strategic point system of resources which is, imo, the best system to ever come to RTS - you don't build peasants to gather resources, your fighting force takes territory which gives you more resources. 
I say, instead of mashing them up, take them apart, so that I can concentrate on the part I need to.  If you keep them all together, it should be a TBS or a very good Diplomacy system like Europa Universalis, Victoria, Knights of Honor, etc.