In the past I too was looking to just use the heatbed as it seemed like a simple solution just sitting there after the print, I then found a picture of a guy with a reprap doing just that with a big mason jar.
After some playing around with different solutions the "Presto" solution is so simple that having that about isn't a chore and I doubt I will change my mind. Ian was right in the first place, damn his forward thinking
One thing to be aware of is the amount of vapour heating acetone creates. The lid on my rice cooker can be covered in condensation very quickly if this was inside the printer you would need some pipework to vent it otherwise all sorts of bit would start to fail. Don't just think a lid will hold it, that'll be pushed off in no time.
Anyway as mine is setup up in my Ikea unit I can't do that anymore which is one reason I tried to get the vacuum method working.
Saying that though, working from Tealvince's suggestion if I could find the right bowl/lid combo I'll give it a try, I wonder if some Pyrex kitchen things would do the trick. I guess having a few different sizes wouldn't be too bad to store.
Also PP stuff should be OK, things like microwave bowls are sometimes PP but I'm not 100% about the direct heating of a bowl, it might go a bit funky rather quickly.......hmmm, that might need some testing.
One last thing, remember the thickness of the container base will make it just about impossible to do a real 6 inch cube as it will start to interfere with the print head, but as I have the same issue with my rice cooker that is a minor point.
Never say never, and never give up trying.