Here's the thing: I've found that when most people squat in a Smith machine (front or back), they tend to allow their backs to round more than they would with a barbell, usually because they don't have to worry as much about falling forward.
In the original post, Noetic was just looking for an alternative to the front squat. Goblet squats are, on the whole, decent alternatives to the front squat.
After having found out that the guy squats 500 for 15 reps at 200 pounds (yeesh), then of course I'd agree that goblet squats might not be the best bet.
Also, in the original post, there was no specific mention of training for quad size. Since that's the case, I'd consider reverse lunges.
Noetic, if you want another opinion, you could try asking Cressey, Gentilcore, or Mike Robertson in their Locker Rooms because they're very familiar in dealing with shoulder injuries.