Plus, I would think blowing up concrete, stone, or metal walls aren't really viable options either...
Any word if this will get an single player campaign at launch?
Currently the modes in the beta are 5v5, one defender, one attacker. Start of the round the attackers drive little drone vehicles into the building to scope out the objective (defenders can destroy) and the defenders prep their defenses by barricading doors, walls, laying down barbed wire etc.
There is a new mode just added today where you play as a team against AI that has varying difficulties. No clue on Single-player.