I have no special knowledge of canon hardware, but not everything can be done in software on special purpose chips. There may not be the necessay capabilities on the chip to display what you need. I agree, it would be nice. I shot a number of exposures of very red roses and learned, as you did, that you can be completely out of range on the red and never know it. Makes me much more gun shy about moving to right.
I have had this problem as well. Lately I have taken an "expose to the right minus a 1/2 stop" approach. I convert the RAW to 16-bit. It seems to be working out, but I am far from experienced.