"Server: we need to write an App Engine server for testing, local development, and potentially production deployment. (Replace Bigtable with MySQL, Hypertable, Hbase, Couch DB, etc.)"
An open-source production-capable alternative to AppEngine (that uses its APIs) would help defuse the lock-in issues.
The Python guys may be happy with one framework... but this is Perl. There's more than one way to do it :)
BTW, I'm a Catalyst core developer, so I'll certainly do everything I can to make working with Catalyst on GAE enjoyable. That's what I want for my applications. But really, getting the web framework to work is the easy part. Getting a Perl that meets Google's requirements is the hard part.
Or, given the timescale, run HTTP::Engine, which is an extraction of the Catalyst::Engine system that's designed to be used by any framework - i.e. to become a perl equivalent to WSGI - and which Catalyst is going to port to once it's baked.