Here's the kicker: once you have become a deep expert in one thing, you can choose at any time to take on a project or client outside your scope--on your own terms. It's the best of both worlds.
An exclusive system makes you dig deep into your experience as a pro photographer and find the one thing you do for your clients that no one else does.
You actually already know what your system contains, because you're doing that thing (or things). The elements of your system are all right there in your own history and one-of-a-kind experiences. You just need to know where to look to dig them up.
When you say, "I need a new website," what you are really saying is, “I have a problem that needs solving.” And sure, a new website might be part of solving that problem.
But when you just go and hire a designer because you have declared that you need a new website, you are not even one step closer to solving the underlying problem.