This is a discussion that probably already happned at some point but I would like to hear from you
In the contract AccessControl the constant DEFAULT_ADMIN_ROLE is public, making it provate would decrease the cost of deploy from 480304 to 475790, a 4514 gas difference (0.93%)
I see why it would be useful to the contract responde which it is using for a role but anyone that needs this can expose it.
This would be a breaking change, so we would not merge it until the next major release.
I think we don't want a PR now, as we would not be able to merge it for a while. We could use an issue that we would tag for a 6.0 milestone.