Yes and no :-)Nice idea SG, but won't this mean that your printer needs to feed dead accurately each time? I've had many printers that don't, and a slight skewing of the printed sheet would knock the alignment out. Just my thoughts, and I may be wrong.
I currently use a 1500W which is pretty accurate. I think a tolerance of .5mm is more than acceptable. Working to tighter margin would be insane. I personally would work to a 1mm margin on live area and would add a 1mm bleed to compensate for it. That would cover it for me.
The alternative would be to trim the sheet after it has printed, this will ensure 100% accuracy every time.
As I do not print coasters this is about as far as I want to go on the idea