3 million homes

Small and large real estate owners are sitting on millions of potential building sites that would be untapped with a simple policy change that has no net change in ultimate taxation.
Currently one can only capitalize on 1031 property exchanges for new acquisitions. The allowance of exchanges for owned real estate would untap idle land and provide millions of units. Exchanging makes idle land construction viable.

Example. Property owner has multiple single family rentals and multifamily land. Owner desires to build apartments, but its financially not viable due to costs, interest rates, etc…

If able to exchange proceeds from sales of existing single family to build apartments, owner would do it and hence create new inventory for market.

Taxes are simply deferred like current exchange.

Sounds quite reasonable.
What time frame would you propose? Would you limit it to only those who own in their own names?
I can see potential for abuse by the same bad actors creating havoc currently, i.e. hedge funds and REITs in the single family rental business.