In case somebody wonders. The „cloud gaming trick“ is, that when you uninstall an add-on or just a package (part of add-on) in a cloud gaming session, it will be remove on your XBox as well next time during startup, apparently before the update check. This helps me right now to „repair“ a broken MSFS installation by removing add-ons to get below a total of 446 installed packages. This works reliably so far and allows for some experimenting without having to delete the entire reserved space once startup is broken. It saves a lot of download time.