MAC blacklist on a per node application

I think this is somewhat antithetical to the concept of the Orbi (and mesh systems, generally). The whole idea is that devices should just connect automatically to whichever AP has a better connection. Perhaps what you need is better AP switching? Maybe periodically the router and satellite(s) should survey all the wirelessly-connected devices and attempt to optimize their connections, so, e.g., if your Chromecast is connected to a satellite, but has a better connection to the router, the system can determine that, and suggest (force?) the Chromecast to connect to the router instead? It is possible the issue is with your device, and not the Orbi, and that your device is the one insisting on remaining connected to the suboptimal AP, despite the Orbi preferring a better AP.