What would it take for anyone to build a "free internet" index?

What would it take for anyone to built a new “free internet” index where every country is evaluated on how free and open its internet is?

This question is inspired by the effort many many countries around the world are making in an effort to age verify, age attest, or simply block content, websites, and digital preservation.

What resources and kinds of info does one need to make an index like this to rank the countries with the most open web and the least. One simple metric I am thinking of straightforward - how many websites does a country has banned/restricted on its clearnet? Are there other metrics and points on which we can evaluate?

What do you all as the community think?

The closest I can think of to this would be OONI but they’re focused on internet blocking only. Still, their dataset could be used as the partial basis for building such an index!

A commitment to maintain it.

OONI, as mentioned by @ch0ccyra1n, and also mentioned by me in another related topic:

I can only speak for myself, but I would not want to maintain a project where my remaining faith in humanity slowly evaporates everytime I look and work on it.

It would have to take into account the reality as well as the laws and also enforcement. When does it stop being the internet and start being just general freedom?