Totally doesn't help you lose weight. It makes a good alternative to snacking, but you're more likely to maintain your weight (as opposed to gain some) than to lose any if you start.
And I've been smoking for about 5 years and haven't developed much of a rasp in my speaking or singing voice. I'm just clogged in my throat most of the time, and can't speak or sing much unless I clear my throat. And it's not giving a good rasp when my throat is clogged, it's purely stopping me from actually making any kind of tuneful sound. So no, that's not a good reason to take up smoking, tbh.