So we can bitch and moan about the inequalities and pitfalls of the current (debt-based) financial system or try to make it more fair, most poor people don't even have access to neither the system nor to mortgages despite informal wealth.

Hence the argument (brough up in De's comment in the diary you linked to) doesn't hold whatsoever (and I have my doubt that it is De Soto's). Many poor people don't own their homes at all. There are no available property rights to the "informal wealth" that enable people taking mortgages. We don't know if people would like to take mortgages - they generally can't.