Immobile only games are kinda fun - I've done two or three. Although of course, some of the Pretenders
still get into the HoF.
Wyrms only would also be rather neat, especially if Arco was Banned for the huge advantage their Wyrm would get. Everyone starting with the exact same chassis, one that is in some ways more limitted than the immobiles. (Not all immobiles are alike - some have nice whopping advantages over others.)