BuddyPress.org

Why change the code? Look into hooking into the main program and changing it via plugins. If you hack the core, you eventually won’t be able to keep up and you’ll wind up with your own custom version anyway.

It might be best for your long term plans to talk to a developer, see how feasible your first-stage ideas are and go from there. No point in trying to do all these things if, like Mike said above, you’re trying to fit a square peg in a round hole.