There's some good advice in this thread, but a word of warning; you can be too clever, or make things too dynamic, and all at the expense of integrity of the application in the future. You can find yourself in a situation, further down the line, where the framework becomes top heavy and it loses all of it's strength as you're constantly developing work-arounds to prevent changes from affecting one or more of the versions within your framework.

There's much to be said about finding a balance between complexity/inheritance and good old stand-alone development; the ideal position is somewhere between the two.