Multi-Account-Containers are great and protect me from tracking to a degree. But opening all sites in the "no container" container exposes me to tracking when I click through to a new unallocated site.
A better approach would be to assume all sites are evil and open them in a new container by default.
Then when I see value in sharing data between sites I can add them to a pre-existing container or create a new one.
At least an option to work this way around would be very handy.
Though it would require a decent timed clean-up process as we would not want to lose cookies etc for a site that was only visited once a year but also would not want to have all these containers stored forever.