When you looked through CoreUnits.xml and looked at <HideInSetupLists>1</HideInSetupLists>, did you miss the tags
<ClothMapScale>1.6</ClothMapScale>
<TacticalModelScale>1.6</TacticalModelScale>
for the units.
I believe weapons scale with the size of the unit, so you would have to make new weapon graphics to get a different weapon scale.
if you plan on going this route, you might have to look at the CoreRaceTypes.xml (these have a large variety of starting units for each of the races), as well as a generic model for each of the races.