I almost went down this route on a project once. As soon as I noticed myself writing an identity map, I slapped myself in the face and just downloaded Symfony.
Funnily, this is the reason I adore Slim so much. In the PHP world, it gives me exactly what I require in a framework, and nothing else. Slapping it on top of a well-defined class heirachy becomes a simple exercise. I like it so much, that I'm porting it to Hack/HHVM[0]!
Symfony is awesome but I feel they try to stuff too much into the default framework configuration. I don't want all those silly annotations, for example.
