If you want a 200m hex, dig somewhere (seems I lost my CD somehow) the Steel Panthers III, there might be Kobhack also somewhere to download to toy with unit stats, but be ready for lower (much, much lower) level of fun
(Actually toyed with SP3 OOBs for a while way back, for example divided all speeds by ca. 3 to prevent the situation when units were able to drive through the whole range of their weapons in one turn, and more). However with current SP engine, I think you might get away with changing scale to 1 hex = 25m (say going for fireteams instead of squads etc), but even there you will expect some mismatches with burst radii etc.