Both of them (Fab and Aly) are worth 20m young and with loads of potential, but I doubt Marotta would spend that much on fullbacks, he'd rather but a 20m striker than a 20m fullback.
Cassani is great, I know there's a trend on this forum calling all Italians average, but if there is a non average Italian footballer these days in Serie A, then it's Cassani, but he's too attacking for a 4-4-2 with Palermo, he along with Balzaretti get's the freedom to overlap, I doubt he'd get that with Juve.
Funny thing how 3 of the best Italian players in Serie A now, used to play for Juve Cassani, Balzaretti, and Nocerino. Say what do you like about Nocerino but he's very, very good nowdays.