DMCA takedowns should not exist. If it's important, get a court judgement, where the opposing party can present a defense.
If it's not worth a court case, then it must not be very important. Or maybe they have no case.
If it's not worth a court case, then it must not be very important. Or maybe they have no case.
A and B now have each other's information, and are free to sue each other.
The problem with the status quo is that the platforms are taking full advantage of the slack given between receiving notice and taking action for counterclaims, but acting immediately on claims.