You'd need an entirely new map rotation script, I think. Then you'd have to write the rotation from scratch with only the maps you want. If you don't want to install an entire admin mod, I think this script will let you customize a map rotation: http://www.chaingunned.org/sling/Various_Scripts/EzRotation.vl2
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http://www.chaingunned.org/sling/Various_Scripts/EzRotation.vl2