Any specific reasons why it's error-prone? I've just seen someone post a link to SPECS in the comments to the post - it's interesting but takes a very different direction. I wanted the code to remain recognisably C++.
I've been programming in Python for 4 years and I've never spent hours trying to find an indentation error.
It comes up, sure, but no more frequently than any other syntax error in a different language and there are usually dead giveaways indicating what happened. Most IDEs/editors have options to view whitespace characters, so if you're worried about encountering a bug from this you can always enable that feature.
Well I've written quite a bit of CoffeeScript, and while I had a few issues with incorrect code translation to JavaScript, I don't recall ever having problems with mis-indented code.
Have you looked at previous attempts, such as SPECS? http://www.csse.monash.edu.au/~damian/papers/HTML/ModestProp...