Blending seems to happen naturally between different textures.
Try this for Normandy map:
[FIELDS]
LowLand0 = land/summer/Compans_Marsh.tga
LowLand1 = land/summer/Compans_french_fields_2.tga
LowLand2 = land/summer/Compans_french_fields_1.tga
LowLand3 = land/summer/Compans_french_fields_2.tga
MidLand0 = land/summer/Compans_Marsh.tga
MidLand1 = land/summer/Compans_french_fields_2.tga
MidLand2 = land/summer/Compans_french_fields_1.tga
MidLand3 = land/summer/Compans_french_fields_3.tga
Mount0 = land/summer/Compans_mountain_fields_2.tga
Mount1 = land/summer/Compans_mountain_fields_2.tga
Mount2 = land/summer/Compans_mountain_fields_2.tga
Mount3 = land/summer/Compans_mountain_fields_2.tga
Country0 = land/summer/Compans_french_fields_3.tga
Country1 = land/summer/whitechalk.tga
Country2 = land/summer/Compans_french_fields_3.tga
Country3 = land/summer/Compans_Marsh.tga
City0 = land/summer/Compans_French_village.tga
City1 = land/summer/Compans_French_suburbs.tga
City2 = land/summer/Compans_French_City.tga
City3 = land/summer/Compans_French_suburbs.tga
AirField0= land/summer/Compans_airfield1.tga
AirField1= land/summer/Compans_airfield1.tga
AirField2= land/summer/Compans_airfield1.tga
AirField3= land/summer/Compans_airfield1.tga
Wood0 = forest/summer/rom_forrestground.tga
Wood1 =
Wood2 = forest/summer/rom_ForrestFar.tga
Wood3 =
Water0 = water/water.tga
Water1 = land/summer/Compans_coastal1.tga
Water2 = land/summer/Compans_coastal1.tga
Water3 = water/rom_fields_Beach.tga,2
S! Comp