I don't know why you'd want a system where a rich person can take the land your house is on if they can pay £1 more than you for it every so often, unless you're a fan of the feudal system.

I also don't see how it discourages speculative investment. If nothing you own is really yours for very long then you're much more likely to have your property bought from under you if it's in a desirable area. As an investor I would want to do that if I believe I could rent it out at a profit.