It has been a struggle to find the optimum maps for the COD2 Stock server so that it remains active. After a dramatic slow in the summer of 2006, we decided to limit the rotation to the most popular maps and concentrate on playing those. Shadow took the lead to identify the ones he felt were most popular and we have pretty much stuck with those since the popularity increased dramatically after the change.
We have 7, not 4 maps in rotation. But based on your request, I decided to do a little investigation as to how our current rotation compares to the most popular maps played by the top 10 teams in TWL 4x4 TDM. Here are the results:

As you can see, we are very close to the optimum. However, it does appear that we could add Breakout and Farmhouse back into the rotation so that we have all the most popular maps covered. We have debated in the past about Breakout because many players have video problems (slowdown) with that map. But since it is in the top 5, I'll add it along with Farmhouse later today.
Old Man Mike