I am interpreting this as the renter cannot prevent people from going to a rented planet and mining or gathering. If this is what you mean then I disagree. One of the reasons to rent is to avoid the kind of destruction that now occurs around major hubs and builds on public planets. Now if you are saying anyone can visit, I can support that. Visiting and exploring a planet does no harm to the renter. It might encourage people to ask to build on the rented planet.
I personally would never take random selection, I might end up with a pink planet and that is not what I want. The key to renting is to be able to make the planet your vision and that includes the colors (not the resources those have to follow rules). I think if you restrict people renting too much, the end result is they create a separate universe and then there is no interaction with the public universe. As the developers have the ability to create any colors they want on new planets they have the ability to counter any colors that are picked that do not already exist, if this creates a problem.
At a certain point it is. . If I do multiple builds it can get very real world expensive to buy all the plots to do this more than once. It also is very time consuming. I realize the rented planet is an ongoing expense, but spending the time actually building versus plotting trees probably makes it worth it.
To your last point, other than access restrictions there has not been a lot of information from the developers so I am not sure how much Admin power they will let the renter have. IN particular if the planet is connected to the public universe.