For example there’s this old thing: https://docs.google.com/spreadsheet/viewform?formkey=dDRKNzd... (Google App Engine VM Runtime TT Sign‐up)
Unfortunately, since all of this effort went into securing yet another runtime (PHP), I don’t think it will happen.
It would be great if at least it was possible to use Appscale over GCE or just the Datastore – which is by far the most attractive feature of App Engine, other than Task Queue – with custom deployment solution.
Google Cloud Datastore could deliver just that if you don’t mind paying twice:
You should be aware that Cloud Datastore has a serving component
that runs on Google App Engine, so there will be instance hour costs.