I do this with a denim sleeveless button down that I have, and it's great! I don't have denim sleeves fighting with wool or cashmere sleeves, and constricting my arms!
I cut the sleeves off the top because it didn't fit me well, but I adored it. The fit problem is one I usually have, my shoulders are too big for most tops. Most women measure up at 14" or so, and I come in at 16". No wonder I love knits! LOL
I'm going to remember this when I see a really cute sleeveless top like hers! I always pass them by because I think "Who wears sleeveless in the winter??" Doh, I can!