Earlier quoted context omitted.
The difference between Android and Google Play Services/Google Apps Suite is, that the latter use Google servers and the former does not. If removing these apps makes Android unusable for you, it means you are hooked on or locked-in to them. Asking for open-sourcing the client parts will not help you anyway, because the server parts are still running on Google servers and you won't be able to replace them.
> Asking for open-sourcing the client parts will not help you anyway, because the server parts are still running on Google servers and you won't be able to replace them. Yes I could, if the average android phone would allow me to do so. You can't go to the store, buy a phone, and remove google play services. At the very least you have to root the phone, which isn't possible on most devices.
What you can do, is to install apps or plugins for CalDAV/CardDAV-like services. The account system works with any generic account, not just with Google accounts; you can implement any service you want talking with any protocol you want. You don't need Google Play Services source for that.
Removing apks for android installation is cannon for sparrows. Remember, /system is not only for running the system, but also for factory reset/recovery too.