The other problem is: we don't want warfare to be the same in every era, and we want to have some kind of historical feel. Artillery should be dominating the WW1 battlefield, until landships arrive.
Armored cars were never a major factor in combat or warfare, and for motorized and mechanized infantry we already have representations of that (3 move ww2 infantry, then the mech inf unit).
Much easier to merge both dragoon and lancer into the landship.