Yes, it would, it's called T shape osteotomy, but I don't know of a surgeon who performs it, although it's technically logical, it's very rarely used for widening.
But an "onlay" seems more straightforward to me, injecting radiesse for instance could provide aesthetically satisfying results, but, as for me, I won't. I want something permanent, and I don't want to mess up with that area with injectables again.
Also,I'm in Europe too, an I know how difficult it is down here to find a middle way between purely functional and cosmetic surgery.
I'm glad you're looking for the same thing as I do, but I still don't get why there aren't more maxillo facial procedures to change the shape of the chin aside from those silicone things, because a deficient chin is often a narrow one as well, and you need to correct defects in 3 dimensions.