If you want affordability, land value tax will incentivize appropriate development.
If you want to steal/take control over land arbitrarily from its users, land rent is a good choice.
In my opinion, if someone owns land and can afford the tax, leave them be. Let them keep their land rather giving it to an entity that supposedly knows better what to do with the land than the occupant.
If you say 'well I control the gov't via democracy'! Well you would control that same 99 yo gov't lease holder too about just as much.
The government is the thing that allows the concept of land ownership. Anyone trying to take ownership will have to go through courts with legislature written by that government. Even if they gunned their way into occupation, getting a court order to have the (often better-armed) police turn it back would be possible.
I see no way around having a central coordinating body drawing up guidelines to define ownership. The ground is a finite resource I don't think anyone should be able to hoard and occupy indefinitely. That coupled with me not liking wealth inequality leads me to think that the Singapore (and others) way of leases might be good in the long run.
Say you buy a 99 year lease and plan to live there 20 years. When you are ready to leave you are selling the remaining 79 years on the lease.
Your improvements should increase the price you get for the remainder of the lease.
While the remaining term on the lease is still long it is not much different than owning (except that you might not be allowed to do things that harm the value of the property).
As the remaining time on the lease goes down, it slowly shifts from being like owning (with similar incentives) to being like rental.
I'd guess that for at least the first half of the lease (in the case of a 99 year lease) and maybe even up to 70 years so so into it there is plenty of incentive still for leaseholders to improve the property.
So you end up with a property that goes through 3 phases. In phase 1 the people living there have incentives to improve it. Then in phase 2 they just have incentives to maintain it (except maybe the last leaseholder). Then in phase 3 the lease has ended and the property is back in the hands of whoever owns it.
Phase 3 is the most interesting one I think. Imagine a development that was all 99 year leases starting at about the same time. When the leases all end the land is all back under the control of one entity. In the 100 years since the development was built a lot might have changed, and there might be some other better use for that land. That entity can then use the land for that.
If the development instead had sold each lot instead of 99 year leasing them, then 100 years later when there is some better use for the land it might be much harder or even impossible to implement that.
The question then is which is overall better? People owning their homes means there is always an incentive to improve the land and buildings. Long term sellable leases means that there is only such an incentive part of the time, but in exchange for that whole neighborhoods periodically become open to redevelopment. That could lead to more overall improvement in the long run for a city as a whole.