I think it is good for the old creative and editing skills that you do mix things up like this. There is much less risk of getting bored (always a killer sign of a duff story that! - or it is with me anyway. I've only ever abandoned one story and it was on those grounds. I was getting bored, couldn't see a way out of it and decided to cut my losses. Sometimes that is exactly the right thing to do. The real problem with this piece was I hadn't thought it out thoroughly enough before beginning to write it and I managed to write myself into a corner).
On my Fairytales with Bite site I've suggested some intriguing opening lines. But there's no reason why you couldn't mix these up and use some as starting lines, others as finishing. You could, of course, do both per line and see what you come up with.
I think the most important thing about writing is to have fun with it. It will show through.