1. Remove density and height restrictions (e.g. "Berliner Traufhoehe").
2. Remove unnecessarily strict building requirements (e.g. "Daemmungswahn").
3. Remove legislation that is too tenant-friendly (e.g. "Mietbremse").
All three serve as breaks to increasing housing supply, the first is a legal impediment, the other two reduce investments.
Doesn't really help getting more affordable flats on the market.
I'm not sure how familiar with the London property market. London is currently seeing a large amount of real estate being built, mostly studio, 1, 2 and 3 bedroom. Hardly luxurious. Prices are commensurate with London income levels. Otherwise people wouldn't live in London.
I feel like most people are moving to the outer zones. Buying flats in zone 1-3 is obviously out of reach for most people, even for most developers not working in The City. From what I've seen, even 1-bedroom flats cost at least £310k near Seven Sisters (Zone 3).
I have to admit though that I was mostly looking for flats to rent, not for sale in the last few months so I'm not an expert.
£310k near Seven Sisters
That's not expensive relative to London income levels, given that property is typically financed over 25 years or so, basically over the most productive phase of one's working life, so it's paid off roughly when one retires. Most young people don't think long-term: they just look at the price and their current annual salary, and see a mismatch.Maybe it's good this way, because unless you realise that a property is a serious long-term investment, and that the target is to save for retirement, they probably don't have the financial maturity to make such a large purchase and should stick to renting.
Note that property always reflects income-levels of the working population. That's because they are the ones that buy / rent property. Rent and property prices are strongly correlated, because it's fundamentally a risk/reward trade-off: when you buy you take on a fair amount of risk: heating may break down, the roof may leak, you might not find tenants in time, tenants may ruin the property, not pay rent etc etc (From bitter experience I can tell you that "may" really means "will"). Tenants don't carry this risk, hence need to compensate for this risk transfer. That's why renting appears to be more expensive.
Focussing on foreign billionaires who buy-to-leave-empty distorts how the property market works. The real question is: what percentage of their income is the average person willing to invest in property / rent. This is remarkably constant.