Right, so you could see that 30 trillion + commercial number as a loan that the federal government is taking out that they only need to pay the interest on as it accrues(as people spend their land tax credits). This is something the federal government can handle, as the system will more than pay for itself over the lifetime of the tax credits.
A tax credit that gets subtracted when the homeowner defaults equal to the value of the default would resolve the walk-away problem.
The issue is the gains in efficiency from the introduction of the Georgian tax system get traded off against the loss in efficiency from more than doubling the national debt. I don't have enough economic skill to model all of this to know whether we end up ahead or behind but my intuition is the effect sizes may be similar in a number of key dimensions.
I agree you can modify how the tax credits work to potentially transfer the mortgage loss credits from the homeowner to the mortgage holder when the homeowner walks away. If you do this effectively you can reduce the cost by nearly $10 trillion but still have around $25 trillion in residential costs.
A tax credit that gets subtracted when the homeowner defaults equal to the value of the default would resolve the walk-away problem.