Just be very careful because Air Marshall "contains" SSIDs that it sees as a rogue network. Care should be taken when configuring SSID blacklist policies as these policies will apply to SSIDs seen on the LAN as well as off of the LAN from neighboring WiFi deployments.
Air Marshal is disabled because the MR70 doesn't have a dedicated scanning radio. If you enable Air Marshal on you MR70's it will enable opportunistic scanning for those AP's.