Interesting theory. What about the people who can't get mortgages ( for whatever reason ) - where are they meant to live if there's no rental property ?
I'm not sure why you think having a second home is "greed". I happen to have a second home - admittedly abroad - I could sell up and use the money for something else. Luxury cars, posh holidays, shares to increase the pot etc etc etc. Or I could just leave it in the bank doing nothing. How is it...
Re your council tax bit. Charging a tax on a made up value of a property - a property is only worth what someone will pay for it - is an utterly bizzare way to collect tax. I say that as someone under investigation by HMRC for allegedlly under valuing my late parents properties.
I'm now going...
Not seen the details but the idea mirrors what some West Country councils do. The key phrase is 'second homes' - i.e. where someone owns a second property as a home so it sits idle for chuncks of time. It's not aimed at BTL market - those properties are not second homes.