One day last week I watched the Today show - well, I watched the Today show every day last week, and every day of the last 26,000 weeks as well - and they did an instructional piece on layering. They took their usual somebody-please-give-me-a-sandwich model and put her in a reasonable top and, alas, leggings. Then they 'layered' roughly 73 other items on top, including a vest, a belt, a cardigan, a parka, a down vest, a hat and a reasonably small blue plastic child's chair. Oddly, by the end of the lesson, this 83 1/2 pound woman looked laughably puffy and wide. So much so that the show's host started to giggle. Thank you , Today Show; lesson learned!
That said, I think this little 'boyfriend' vest (does your actual boyfriend wear a vest with a shirred back panel?) over a tailored blouse and with a skinny belt would make an attractive ensemble - with actual pants of course.