I've always thought of YC as more of an incubator for young 20-somethings trying to get an idea off the ground. The impression has been fortified by the reported small amounts of 'seed' that is given out. I know a lot of people in older age brackets (30s-40s-50s) with a family and Silicon Valley mortgage who have great ideas and experience but wouldn't even consider approaching YC.
My one suggestion is if you want to expand your age/experience bracket and get these people to apply, you may want to address issues directly relevant to them. One suggestion is to relabel the investment to something more like a 'stipend' and explain clearly that it's not expected to cover salary and life expenses, but only to help defer company expenses. That way, people know that they need to set aside enough savings to cover their family.
The other is to spell out clearly the policy of working on outside projects (to bring in some money) during the YC 3-month period. Leaving it ambiguous keeps out people who need a part-time gig to bring in some money but could spend the rest of their waking time working on a cool product.
I know people who work as consultants and make $10K-$25K in a month. To these people, the YC 'investment' is more of a deterrent. The main attraction would be to get wired into the network and tap into the experience YC and its alumni can offer. It would be good if you could clarify whether it makes sense for them to apply or not.
Overall though, a good write-up with a decent level of detail. Thanks for putting it up.