If you're writing a DS novel in hopes of actually having it published and making a profit from it, then by all means, you'd better keep the characters the way they were originally written, and don't let the plot stray too far from the Collinwood we all know and love.
But if you're writing for the love of it, because you have a story idea you just HAVE to explore, and characters you're dying to bring to life, then write what you damn well please
Personally, if I was to write such a novel, the opening scene would be the one where the Collins family is burying Barnabas at the crossroads of some major intersection in Maine, accompanied by the Rite of Exorcism being intoned by a Cardinal, at the very least.
But that's just me.