> Or ... block all the IP addresses of Google App Engine, at the risk of blocking many applications. having nothing to do with tracking.
Anyone hosting legitimate apps in the Google ecosystsm is indirectly complicit in this and at least for my personal network, I have no concern with blocking Google App Engine holistically.
Additionally, I think it's important to hurt Google as much as possible for escalating in this way. Widespread blocking of GAE may seem extreme but it's also arguably warranted.