Wow, many assumptions.

1. JKR has said that there are laws about what you're allowed to create with magic.

2. I think you're over-estimating wizarding skill and underestimating the difficulty of magic.

Harry is a slightly above average student. I very much doubt he could transfigure clothes. I'm not even sure if Hermione could. Even in their OWL exams they're still not really very good at Transfiguration - the transfigured objects still partially resemble their previous state, and they're still very small. Clothes are pretty large.

Remember: most wizards can't even cast a shield charm.

In fact, if we see Transfiguration as merely a massive load of spells which detail every possible transformation, then to stop people making clothes all you've have to do is not teach the ones which pertain to clothes.

So no, it's not reasonable to assume that most wizards would be capable of making clothes.

Thirdly, we've never observed a single transfigured object revert on its own.

Fourthly, we're told that transfiguration alters a thing in-itself, rather than overlaying a magical effect (which would be a charm). The magic is in the transformation, but once the transformation is complete then its done. So if you change a rabbit into a fish, once its a fish there isn't any magic keeping it a fish: it's just a fish. This apparently removes any room for reversal without reverse transfiguration.

 

If that was true, then human Trasfiguration would be essentially a murder. At least the victim would lose magic and all memories of his earlier life (especially if he was Transfigured into an unliving object). Yet we have seen people turned into animals and still remembering everything and in the case of Animagi even being able to reverse the transformation.

It's quite clear that Transfiguration doesn't affect soul and whatever that is the source of wizard's power.

 

Being an Animagus is different from being transfigured, in that an Animagus retains it's mind. People who have been transfigured, don't.

Found the exact quote.

 

More like borrowed. I'd bet my left nut dementors were inspired (at least partially) by Tolkein's Nazgul.