Strictly speaking, there's no nessisary perquisites for Improved unarmed strike (or a level in monk), and dex is more important to a spellcaster than say, strength. I can see him using some of his feats to give himself improved unarmed strike, even if it is kinda useless for a sorcerer (a sorcerer close enough to punch someone is in a bad spot). 

It's not the most optimized way to play a sorcerer, but as hey. Thus is all for good fun, yeah? I mean, I'm a half-orc druid. I'm not exactly optimizing either.