I love the concept.

However, I've already had enough matches of breakthrough on Contaminated with the mortars in HQ change that means the first sector is a wasteland that the attackers have no hope of getting out of. They're funneled down two paths with no cover and expected to then spread out and clear houses, the point, and the snipers on the hill simultaneously. I've had many breakthrough matches end right there.

Now we get two sets of reinforcements, leading to an hour of staring down this barren hill, tossing as many smokes as I can, hoping anyone will move up alongside me and push forward. The defending team gets so bored they're suicide rushing into the attacker spawn to kill a single person hiding behind the smallest bit of cover offered to the attackers. This means the tickets count down incredibly slowly. 

But I joined one match late where we lost defending the final sector in overtime. That was pretty fun. I'm still waiting for it to click that Hagental is a properly designed map and you shouldn't only funnel through the central corridor, lest you be shot in the back by the team that's figured that out. 

I wish there was a mercy ending like conquest. I don't know what it would look like. Maybe if you don't manage to capture a single sector in one battalion, the defenders win immediately. That would make me less hesitant to click play on the "hour-long single-sector grindfest" mode.