I'm always willing to take a fresh look at tools other people like. There was no VIM mode back when I used PhpStorm, so that sounds interesting from that aspect (as does the sublime vintage mode). But should qualify that I'm not naive about this, have spent a lot of time in IDEs, and used dozens of different editing environments over the years. Back when I was a C++ programmer working for another company, I didn't have a choice. I also used PhpStorm for a couple weeks when it was new (with ProcessWire), as well as Zend's IDE for some time. I even grew up in Turbo Pascal and Borland C++ IDEs, using them for years. But my mind always ends up more in the editor than in the code. For me, less has always been more. It's not about what's practical, easy or fast. VIM takes me to a place where I can think, and it took me years to find it. I lose creativity and enjoyment when you take away the minimalism. Coding becomes about work rather than code. I lose track of stuff when something is keeping track of it for me. What can I say, this is how I am about all my tools except maybe Photoshop. No doubt IDEs can be time savers when it comes to certain tasks, but I've not found it worth the tradeoff. (Though TextWrangler is my go-to for anything involving regex search/replaces across mass amounts of files). I will keep trying out tools that other people like and recommend, but I think most of the time we're looking for different things. I'm not trying to sway anyone towards using what I use. It's not practical, and it's slightly insane. In fact, I would say you should avoid the likes of VIM if you enjoy using an IDE.
This is all beside the point on PSR-0 changes to the core. I can put up with more files, as the inconvenience is relatively minor. But I thought it was worth asking if there were any compliant conventions for including a similarly-named group of classes in one file. For instance, a file named Selector_.php might include classes beginning with the word "Selector", which are already grouped together in a file by intention and design.