Haha, all this time I never knew the ? blocks worked like that... and I searched and looked at 3 walkthroughs just now, and even they don't mention it! But I'll be using this trick next time I play the original.
It doesn't seem too difficult to implement, but I might open a can of worms; one technique I read for getting the most out of the ? blocks is to skip the ghost, by punching the ? block and making him appear, then punching 2 star blocks to make 2 bags of money appear, which causes the ghost to disappear, the way money bags do when there's more than 2 on screen at once. People might be expecting to do this as well. Adding this behaviour would add more code memory and might not be possible without refactoring even more. I should probably just update the page to add more specifics on the differences!