Just in case someone still here , it's been years since i last touch this game but the following is the solution to some of the issue .

The issue with the unit card not highlighting : go to ui/units/icons , remove the background of the Png and put in back in you'll be good to go .

If you encounter any problem with the javelin animation
( not appearing in hands while they aim it )

1.go to variantmeshes/variantmeshdefinitions

2.Replace the <SLOT name="weapon_4" /> to the following :

<SLOT name="weapon_4" attach_point="weapon_05" >
<VARIANT_MESH_REFERENCE definition="VariantMeshes/_VariantModels/man/weapons/javelins_leaf.VariantMeshDefinition" />

a javelin model should display properly but not sure if that was the original one they throw .