I would recommend building a mortar or flamer against IS, just a suggestion.
Perhaps tie the bonuses given to the type of cover?
E.g. bonus for being in green cover > bonus for being in yellow cover?
This is already the case.
You can also destroy cover to create killzones. Buy minesweepers and spam destroy cover to limit their options in open areas. A great place for this is the graveyard on semois because you can deny your opponent heavy cover while keeping it for yourself. But you can do this all over the place.
Also keep in mind that units like pioneers are actually really cost effective against Infantry Sections, and can win fights up close.