A problem with defensive structures as tank-traps, mines and razor-wires is that it is often simple to move around. Tank-traps and mines seldom have a big impact on the game. Razor wire often comes in larger numbers, and thus are generally more usefull I would say. In some situation you also have lots of mines, and thus give some value for the defender. But often, its no big thing. And if there exicst mines, they are extremly seldom steped into. That would be extremly stupid. You dont want to enter a mine field, regardless. Cuz they kill both squads and vehicles. That is fair and square, but this also makes them difficult to use in scenarios I guess, cuz if mines actually block something, well, then they might be overpowered. Maybe unless the enemy has engineers and 'remove minefield'. If thats not the caze, forcing an enemy through a minefield is simply to devestating.
Therefore I have one suggestion how one can improve mines: you make real and fake mine tokens, which looks identical on one side. Then you place both fake and real mine tokens on the map. The real one could for example be place 'at' random among the available locations, and are only revieled by the attacker when a unit enters the hex. If for example one out of three is a real mine, you could place a lot more minefields, and the attacker would never realy know where the real one are. This would do a few things:
1) mine fields would not be as simple to avoid, cuz you dont know exactly where they are
2) since 2 out of 3 fields are safe, an attacker would eventually risk steping on one. Or, you might make scenarios such they are forced to do so, without completly wrecking the game.
For tank-traps to be efficient, wise placement is imortant. A random tank-trap along a random road would do next to nothing. Maybe except for slowing down trucks, which they actually might be preaty good at when I think of it.