Both labour under a fallacy. Designers everyday of the week are coming up with ideas to increase density and build more housing. But each is a drop in the ocean and London’s housing gap keeps getting bigger and bigger. The fallacy is one of com position. Every rooftop could be built on. every social housing estate redeveloped etc. But each of these has a cost and to universalize them would require massive state spending and massive state interference with property rights, as well as an unfeasible number of compulsory purchase lawyers and court dates to take up the 100s of thousands of affected property rights. If it was going to happen it already would have, and already is happening to the maximum extent given current resources.
If you want to show extra capacity you need to show strategic design solutions that are deliverable, on sites that are suitable and viable. If you cant show this then its fantasy stuff. Continuing to peddle such thinking is institutionalizing the problem, a lack of strategic planning to effect change that will deliver new units in suitable numbers, thinking a quick design fix here and thee will solve the problem. It wont we have tried that and had 40 years of failure. So lets try something else we know works in every growing city in the world, large scale new housing zoning and delivery – there is no other answer.