RE: Using Blockchain To Sue Someone In UK

This has great potential. Not necesarily in this form, but in a way where both parties are known.
There could be a new address for every case. Then the lawyers could send every documents and other materials to the case address.
This helps immutability and transparency if you know the case address. Separate addresses for every case could help in organizing things.
Just an idea of course, but I see this as a future possibility.