The OAV is very... round. I hope the emphasis on roundness wasn't a cause for the delays in the last two episodes.
There is much there that wasn't present in the show for fans of... round, though.
One last word on safety: I still think the girls would have looked cute (and a lot safer) in proper uniforms. I liked Katyusha in her giant chibi helmet. Having extremities outside the tank would still be a safety risk.
It would have complicated the narrative, but I could also see a safer playing option where the tanks are actually using
MILES and all of the explosions that we're seeing are computer-simulated for the spectators... because when we're watching the match we're seeing on the big screen like the people on the bleachers.