Is it possible to set limits to the number of user signups per subsite according to subscription lev

I want to offer subscription levels for my Pro sites clients which would limit the number of users who can sign up for their subsites.
Example:
Free level: max number of users: 10
Basic level: max number of users: 100
Pro level: max number of users: 1000

User activity is pretty predictable because this is a promotion service, so it makes sense to offer packages to clients based on user numbers.
Is this possible in any way with pro sites?