>* allow for multifamily housing
Zoning is entirely a local matter, so sure, talk to your local city / county / state if you prefer there to be more allocation for multifamily. It isn't something that the feds have any control over.
>* remove the mortgage interest deduction
So what's your goal here, given that historically this was the single biggest tax benefits to the (ever-declining) middle class.
>* implement land taxes instead of property taxes
Real estate is predicated on the concept that adding value to the land increases its value. So... what exactly become the merit of taxing land over property? If you tax property, the value of the land is included in that tax.
>* have the Fed stop purchasing mortgage backed securities (in the midst of a housing bubble)
Real estate is local. I'm sure there are markets that are in a bubble, but that doesn't mean that every market is experiencing that.
>* get the government out of the mortgage securitization business
These programs by and large benefit the non-wealthy by providing a degree of stability in the mortgage market that make it worthwhile for lenders to lend. Wealthy investors generally don't care - they are paying cash, working out seller financing arrangements, borrowing from hard money lenders, or have long-term bank relationships such that they have all the access to conventional money they need. It's the less fortunate and middle-class that get hurt when government programs are restricted.