Need help in creating a certain kind of subscription?

First of all, congratulations on the awesome plugin.
It has helped me in setting up some good digital stores websites.

However, lately, I have been stuck with a problem and need help with a membership website I am trying to build.
I just want to know whether this is possible using EDD and it’s extensions.

I am trying to create a membership website where members buy monthly subscription plans and in return get access to a PREDEFINED number of FREE products. After running out of their monthly quota, they can buy the digital goods by paying a price per product/download.

So let’s say the monthly plan is $50. A customer named Jor buys this subscription plan. In return he gets to download 20 ebooks for free per month. If he has crossed his download quota of 50 downloads, but still wants to download another ebook, he can still do so. But now he will have to pay $5 for each additional donwload.

After the monthly cycle is complete, his download quota again resets he can again download 50 ebooks for free in the new month.

Is this possible using any extensions(paid or free)?

The closest implementation seems to be given here. But it does not account for monthly quota limit.
By using the solution given in the link I would be able to give the customer unlimited downloads. What I want is rather opposite-limited downloads per month with the option to buy additional downloads at an additional cost.

Any help would be highly appreciated.