Some of these ideas sound interesting and could open doors to other options.
Right now the main reason for the auction system is to make the land trade more dynamic. In the old system it was quite easy for a player to stockpile money and hold onto land for a long time though right now the system can still be exploited some by those players with high amounts of silver. This though is one of the reason's why I am happy for the building demolish and downgrade features that save some of the player's hardwork from a buyout.
There were in the past other ideas thrown out on how to have land transfer such as allowing the guild owning the city the option to evict players but I do not believe that idea was well liked.
The reason why in the current system all plots go on sale at the same time is simply a safety mechanic to protect against the very rich tychoons who attempt to buy up too much land. If you have a bunch of players all dedicating large sums of money to a vast majority of plots it becomes increasingly tougher for a single tychoon to hold onto every plot.
Now if you imagine that there are other factors in play that could prevent a plot from going to auction that means tychoons who have managed to collect plots will beable to have less competitive buyers.
There are also difficulties in how to handle things like well what if the owner of the plot chooses not to build anything? or if he sets the taxes so high to prevent others from using the buildings so as to preserve the food.
Ideally what SBI would be looking for is an idea that follows these points:
Ensure plots eventually change hands
Allow fair room for players to have some RL obligations come up that do not automatically mean a loss of property.
Make it difficult for single players to own massive quantities of land.
I do not at all believe that the current system is the best way of obtaining these points also just to add that the above points are from my memory and interpretation of what SBI is hoping to obtain with city plots so please do not take those as official statements or anything from the AO team. Back in the summer alpha of 2015 before the land was changed to this auction system I was talking with a guild who was quite set on buying up some plots and taking pride in owning their own little niche in a city but when the change took place they abandoned that idea in fear of larger guilds just snatching up their buildings and land. This threat is very real in the current system and I would not be surprised if it deters many individuals from taking part in any city land ownership. I guess I will end this book here and hopefully more ideas can pop up or more discussions.