It's a fine choice for a cab, but really... unless you're building some type of smaller cab (cabaret, cocktail, mini), you won't have any problems fitting a normal ATX case in a cab. You could also just decase a full PC to save some space.
As for the shuttle, it gets a little warm. I keep SmartFan on to keep the noise levels down, but I'd be concerned about throwing it in a cab with SmartFan on. You probably want to have the fan on high in a cab, and the fan on high is not exactly silent. You definitely wouldn't damage anything, but for a cab I'd put the fan on high and make sure you have good ventilation in the cab in general.