Exactly how much control do Transformers have over their molecular structure? If they can cause parts of themselves to emulate a soft, comfortable leather interior, then.......could they make the wrong mental command and just turn ENTIRELY leather and just....flop....into battle? Now that would be embarrassing.
I doubt it would be possible in the Movieverse. But if it is to appear in the Next film, Then it should be like a joke or something.
Probably not. Remeber, they're sentient machines: When they scan and stuff, that is generated by their computer, and it remembers what is what, what feels like what and what goes where. When they transform, (this is just me thinking) the conversion is guided by a secondary computer not guided by their active consiousness. It's like breathing to them. They do it properly by instinct. Mind you, this is a highly advanced alien race, so these mix-ups probably never happen.
Also keep in mind that movie-verse-formers are said to use local materials to create their alt mode. I doubt a mechanical being would be prepared to turn metallic liquid into an organic compound (remember, Leather's basically processed cow skin). It'd be far more likely that Jazz slaughtered some cow off-screen to get his fancy seats. >.>
Being mildly serious on the subject i think its more or less a case of their mimicing the leather, glass and stuff. It may look and feel like it, but its not. Would be hilarious though if one of them screwed up in that respect haha!
If a TF scanned one of those septic tank pump trucks, do you think it would replicate the poop in the tank? I wouldn't want to mess up that transformation.