I love this facility but would like a simple improvement.
During testing I like to be able to prevent users from subscribing.
The simplest method and one I have used with an equivalent piece of software was to be able to set the value of this parameter to a value that means no more subscriptions. I n the other package this was by setting it to zero. As this means unlimited then maybe a value of -1 or similar could prevent the plan being subscribed to.
At present I have to resort to unpublishing the plan which is not ideal.