A less-obvious solution is to reverse the tenure clock. New hires have seven years of tenure, starting their first day on the job. Aside from gross negligence, they are untouchable. They can follow their ideas wherever they lead. After seven years, tenure is revoked.
Such an interesting thought experiment. What bravery might that initial seven years of untouchability produce? What creativity would it inspire? And how would our expectations for the post-tenure period change if our careers began in an environment of risk-taking?