I've been looking trough the maps you have, and have found that some RA2/YR maps have gone missing. I can understand that some are missing due to being unbalanced and/or being a remake/demake of a RA2 mission. An example would be "DC Uprising" due to a player being only accessible by 2 bridges, and obviously a remake of a RA2 Allied mission. Others, for which I'm unable to find a possible reason, are also gone. A map I always liked from YR was the 8 player map "Powder Keg". A large island city map, which offers pretty much every possible tactic, be it naval, urban warfare, or just tank spam.
Any reason for their removal? Or where they really that unbalanced for MO standards (which would surprise me seeing as some maps imho less balanced then "Powder Keg" did remain).