What is a good strategy for maintaining a generic framework and then using/modifying this into a framework that is used for each project I work on?

In my mind, I would like to have general, generic framework which is not tailored to any given project, but contains the foundation for a project. This would have the generic toolbars, form control hierarchies and the rest. I would tweak this over time.

For each application I would then copy or subclass this framework. The framework would be modified to (or subclassed) and tailored to the needs of the specific application requirements.

How do I do this? I have some ideas, but none seems perfect.

1. Have a main framework. Then physically copy the framework into each new projects directory as I start them.
Pros: Simple.
Cons: Any tweaks to the generic framework will not ripple through the application specific frameworks.

2. Have a main framework. Then reference it from each project. Subclass the generic framework classes into an application set of classes.
Pros: Changes to generic framework are rippled through to the application frameworks.
Cons: The application framework is flat. Changing the behaviour of all types of buttons requires changes to each subclass of each button type (for example).

Is there a better way to do this?