modest nature at +1 should kill many ground types as they are usually weak in the SpD department
*nods Though would you want to give up the speed from a Timid for that? I guess though if you want to have a all out attacking that could work. I myself am really liking the one I posted early as a lead, with 2 entry hazards, Clear Smog to do damage and stop set uppers, and Power gem. But your idea of Modest would work best with a HP Ice, though then Steels give you an issue.