Mercury is actually one of the best if not THE best candidate for terraforming in the solar system, crazy energy availability, metal ore availability, a solar shade around mercury is easier to construct than Venus ( its much smaller and the L1 point is closer to mercury than L1 Venus is to Venus) and its much easier to launch material from mercury than from Venus (fucked surface conditions making insitu resource mining impossible and higher gravity well). a atmosphere would be easy to give too because there's a 1 km thick graphite layer which can be powerdized and mixed with regolith and exposed to the day side and it'll reduce the metal and release co2 which can then be cracked into oxygen and the graphite reused.
come home...