It's interesting that you attempt to measure default risk. I've always considered that as an equity investor quantifying default risk is of little value; by the time it gets to that stage equity will be severely impaired. Of course I get your point about a company needing to be a going concern, but wouldn't that just present itself while analysing earnings risk? I guess what I'm saying is my investment threshold is a bit higher than "will this company be around in 4 years". I assumed your own risk profile would also steer you away?
Agree on the rest of your post, especially on the earnings risk. My biggest investments are always in companies with high recurring revenue streams, so the 99% of time going into assessing the sustainability and direction of earnings is something that definately resonates with me.