I have tried a pre-built stylist/hobby inventor in Twinbrook until he set himself on fire sculpting a metal statue and crumpled into a pile of ashes before I knew how to help him. I was surprised to see that the fire alarm did not go off when his burning backside was hopping around directly under it, and i found that you can not put out the fire by jumping in the bathtub (needless to say that he did not have a shower).
I don't know whether you play with testingcheats on, but whilst inventing one of my Sims set himself on fire and he was a fair old run from the nearest bathroom so I just cancelled the 'on fire' negative moodlet from his moodlets and it put out the fire. Someone else posted much earlier in the thread that their Sim died from fire through inventing, and initially I assumed it must have been a large fire (didn't have Ambitions at the time) but my Sim was on fire the way you described, with his backside burning and him freaking out. So I guess I saved him by simply cancelling the moodlet?
You should make a movie with your blue sims. It would be funny though, with the right music. 'I'm blue, dabadedabadaa...'
lol I'm not making blue movies! But that song is now stuck in my head

I may write up the story of the family though, except I've taken hardly any photos.
So the big question is whether the Ambitions expansion is worth buying for semi-fans(not huge fans) of Sims. Or should one wait for the price to drop?
I love the Sims, and when TS2 was out (and the original Sims) I bought the expansion packs immediately, I couldn't wait for them. With Sims 3, I had no choice but to wait for WA since I didn't have a computer capable of playing it. In fact when I bought WA it was sitting in my house waiting for our new computer to arrive. I saved about £10 or so waiting for it though, because I bought it about 2-3 months after it was out. With Ambitions my friend bought me a gift card so I already had £10 off, only paid £14.98 for it and that was the day after it was released. If you actively want to try out the new professions or the new skills (and laundry!

), then get Ambitions. If you can wait a few months for it to come down in price it'll be more attractive as a proposition. On the other hand, if you were going to get it for the chance to be self employed, the patch covered that. I believe the update Ambitions came with was essentially the same as the one EA issued when Ambitions was released.
If you're a semi-fan, maybe waiting is the option for you. You'll only have to wait a few months for it to come down in price, it's not as though the game relies on the expansions to keep it going. The beauty of the Sims is that it'll only get boring if you allow your gameplay to stagnate, and you can easily shake things up.