Yes, I've hurt my ankle numerous times while skiing. A full out, serious, level 3 sprain does not take 4 weeks to heal. Think along the lines of 2 months, minimum, up to 4-6, to properly heal everything that you've managed to fuck up. Serious sprains are nothing to joke about, you're damaging some hard to heal ligaments and tendons.
That being said, this theory of having your boot act as a 'cast' is only about 50% correct. Do them up as tight as you can without completely cutting off circulation, in a stiff boot, and you'll be better off. A soft soft boot like a 1080(not pro) or a rossi soft won't work as well. And since you do need to flex your ankles to ski properly, you can start to imagine the pain...
After doing my ankle in and rehabbing it for a month, I quickly found out that lots of soft snow(15+cm), jumping, and really tech, sketchy skiing was too much to handle. High speeds were fine, but carving a decent turn was a bitch. Groomed terrain helped a lot. Rails were still ok, oddly enough. Basically, if it was fun before you fucked your ankle, it's gonna suck for a long time before you can do it well again, and your ankle will probably hate you.
Keep up with the rehab, and if one there's one thing to look forward to, it's this: your ankle, despite all I've said, will feel better after skiing than before. It will like the exercise, provided you don't try to go hardcore on it right away and blow it apart again.
'lets all go to hell for having sex!' Lateralis
'jib_this why are you such an ass? all your posts are dissing someone els (sic)' Krongos
'I can't type, I've been drinking' Nolan