There is no way to "undo" what has been done due to poor planning and little to no structure behind the warehouse idea.
You can not simply go and remove the warehouses from those that aren't in "official" groups nor is it a good idea to say that you are going to limit it to official groups only. What does that mean for up and coming groups? They also have potential and should be given the opportunity to own a warehouse for competition sake.
A large official group can be undermined by the smaller group that owns a warehouse by careful planning and work. That's what it's all about isn't it? A competitive market? If it is limited to only official groups, that leaves all of these smaller groups in the dark with no purpose.
Sure it can be seen as "motivation" to get to an official status to be able to own a warehouse, but by the time they do that the current official groups have already taken over most of the state with the money earned off said warehouses. At the end of the day there's a limited number of warehouses and to restrict them even further to only official groups doesn't seem too worthwhile.
Sadly the property prices for the warehouses was seriously overlooked and should have been far greater given the amount of money one of those can produce but it's too late to make a change to the value without upsetting all of those invested in their warehouses already so you will have to let that slide.
If a solo person wishes to own a warehouse and they are going to run the operation solo, well so be it and why would you stop them?
If they are given a way to "employ" people that can be granted access to work with the warehouse, then that system would be perfect.