Don't get me wrong, that would be great, but you didn't outline a mechanism by which MIRAS increases social housing provision. I don't think there is one. Arguably the causality runs the other way as tax giveaways to homeowners reduce gov't revenue and spending.
If it’s more affordable to own a home and there’s healthy taxes on second ones and investment property than you cut out private rentals. Not that hard right? There’s also a higher tax if you own your home outright.
Handily left out the 30% social housing part?