No, Libertarians would not support this. The reason why there are empty properties is that there are capital controls so severe that it's more lucrative to buy a house (and not rent it) as a store of value than a currency/stock/precious asset (gold,bitcoin etc). A law -- which didn't account for the second-order detriments -- created this perversion in the market. Adding another law -- which again won't account for the second-order detriments -- is not going to fix it. Less is more, when it comes to economic law.