Why not just have a target on top with some sort of spring loaded arm that when the target falls back/forward it lights up a red siren light and kills power to the vehicles weapon? Does leave the sides open, but if someone was to flank it and push down this "arm" it would be the same as someone running up and putting a charge on it? Much like we do for large vehicles?
"The hydrogen economy car from the people who brought you the 'Hindenburg
'" - Glen Foster
Condoms do not guarantee safe sex any more. A friend of mine wore one and was shot by the woman's husband!