Here's how I think it's supposed to work:

At the beginning, everyone will have their own RC pool based on how much HP they have powered up. This is the system we have already. The extra functionality comes because we'll be able to delegate our RCs to other pools, so technically dapps could pay users to delegate RCs to their pool should they need them.

The owner of every pool has 100% access to that pool. However, they can give other accounts access after the upgrade. This access can be limited in any way the owner sees fit.

For example.

I have a lot of RCs in my pool, so I start letting other people use it. I can choose who and who is allowed to use my pool, and I can choose how much of the pool they are allowed to spend. The super cool thing here is that I could give 1000 people 1% access to the pool. So on average each user will use far less than 1% of the pool, but those who need more can use more. This allows me to allocate x10 more resources to ten times the number of users. If my RCs run out everyone using the pool will be shit out of luck and need to wait for recharge or find another pool to draw from.

If you run out of RCs you could just change the rules so that users only have access to 0.5% of the pool or even less... or you could target users that habitually drain everything and cut their bandwidth individually.