this sounds like a very ambitious goal looking at the possibilities and features modern (web) frameworks offer
To find a point where to start, you should probably think about what your framework exactly do and what it should do better or another way than already existing frameworks. How should your framework be used? I mean JSF and Struts already give you so much power you should have a good reason to try to create another framework combined of those! Where do you think yo get advantages when you try to combine JSF and Struts? Isn't this only counterproductive?
I think there are many, many more questions you could ask about your idea. And I guess the answers for the most important questions (in your opinion) should clearly show what's the point of your framework at all and what are its key benefits and features. Maybe these topics would be a good area to start. At least I wouldn't consider too much low level details like internals of the JVM and Tomcat at the beginning of such a project.