Any default setting in any browser can be hijacked. It doesn't matter if its a button or a home page or a speed dial or whatever. I work computer technical support, believe me. Anything can be changed and I have run across it more than once.
That said, their are extensions that can replace your speed dial button with a home page button. As the whole point of having extensions is to allow people to customize the browser I don't think there is a need to reinvent the wheel. Just install an extension and go with it.