Anyone who wants, means anyone who want up to a preset limit. The key factor for the publisher is the preset limit. At this time, I think that would a publisher would reasonably permit might well have some near relationship to the number of people here who would be interested. For the publisher, the question is 1/ the overall use--the number of places available times the probability that any one of them will be used. 2/ whether it will draw away the basis of other subscriptions--for example, if everyone at a particular college decided to get access by becoming active Wikipedia editors. I think this unlikely, and I hope the publishers will realise this. To the extent people sign up who do have access elsewhere, that would be a problem for us if it shut other people out, but he publishers would love it. They'd get paid twice over.
There would be no caste formation if the arranged limit is not used., which is what I expect. Removing people from the list who do not use the resource is an entirely reasonable way of keeping the list open to newcomers. It might of course happen that 10,000 people would want to use these resources to write Wikipedia articles. This cannot be accommodated by my proposal, but If they actually did so, WP would be so much better off in multiple ways that we would well be able to find the money to renegotiate the contract; the publisher would be delighted to do so. All such contracts are renegotiated from year to year (or 2 or 3 -year periods) based on actual use. If the use goes up, more money is necessary. If it remains very low, the question is whether the resource is worth paying for at all. As for the legality or advisability of confidential negotiations about the cost, the entire industry works in this manner. Most librarians are unhappy with this, but almost all publishers insist.
If people attempt to cover all problems, people never agrees on a contract. I imagine every publisher would see this as an experiment, and so would we.