Hello! Unfortunately, we have such a drawback to our Resources system now. The issue is known, and we may somehow optimize it in the future, but currently, there are no such plans.
Another option would be to be able to trade in all the extra blueprints of maxed out mechs and weapons for A coins. Just like it costs 240 A coins per blueprints we should be able to change blueprints for A coins. And the amount can be depending on rarity of the mech/weapon.