Most such tactics are explicitly illegal in the UK, unfortunately. Basically, the legal framework for labour strikes in the UK is set up to maximise inconvenience to the public and minimise the tools (and effectiveness of those tools) available to the workers and their unions.
The technical challenges are vast, is the long and short of it. But it's high time there's a good discussion over how it should (or might) work, at least the kinds of properties such a system should have.
Self hosting of federated credentials should be possible, but not required
'Backwards tracking' of federated credentials should only be possible with limited requests (e.g. 'verify author of post') and approval of the credential owner
All data on the credentials instance should be properly encrypted
All data on credentials instance should be fully and easily portable to other instances via common protocols
There are several issues involved here, beyond just 'mere' technology, that need addressing. Personally I think a good start might be to engage with public libraries here. They already keep simple identity records (library cards) and have public service purpose well-aligned with the concepts of the federation and public distribution of information and knowledge.
The purpose and function of the police and the courts is the protection of capital from the people. Some cases illustrate this more clearly than others. This is one of them.
Most such tactics are explicitly illegal in the UK, unfortunately. Basically, the legal framework for labour strikes in the UK is set up to maximise inconvenience to the public and minimise the tools (and effectiveness of those tools) available to the workers and their unions.