Feature request: Autogenerate mode that does nothing

I have a system where proxies are stored in several different locations. The proxy autoloader system provides a perfectly reasonable way of dealing with this, but AbstractProxy::getProxyDefintion gets in the way: its behavior is based on the proxy autogenerate mode, and all the modes that deal with files `require` a specific file. In other words, I want to configure for AUTOGENERATE_NEVER, but _also_ just leave loading the proxy up to the autoloader.

An additional autogenerate mode that's just a no-op would accomplish this very simply.