Against MMW version of the MRM-KE, both ARENA and VIRSS would have no effect. While VIRSS might have an effect against the SAL version of the MRM-CE, but it wouldnt effect the MRM-KE.
Iron Fist though, is claimed to be able to deflect KE rounds. It use explosive projectile shot at the incoming rounds. Explosion should be able to deflect KE rounds.
Again basicly this Iron Fist works like ARENA. Improved target acquisition though. And tank caliber kinetic ammo can be anything from basic AP to APFSDS, so I am not investing any money on it.. yet
I don't know if either of you guys are still working on FCS icons and units but here is a somewhat recent update on FCS showing some good concepts of the vehicles on page 11.