Eliminate it altogether. In our litigious society, the protection from reprisals that tenure once offered is no longer necessary.
Move to a more transparent model: tenure as a black-box process is terrifying and inefficient. The only thing worse than moving the goalposts is hiding them entirely.
Hire professional management to run academic departments: good management would help more folks attain tenure, and have a better understanding of why they fail, if they fail.
Cut it down to size: Offer tenure in 10-year chunks, rather than in perpetuity. This will help maintain performance and allow for regular reviews.
Standardize the expectations within departments, and state any changes to those expectations when adjustments need to be made. This should be public and on paper.
Offer a choice between a significant raise and tenure. Could be especially interesting in combination with #4.
Create databases of student ratings that can make expectations more clear, both for pre-tenure faculty and those assessing them: if Class X traditionally receives much lower student ratings than Class Y, all parties should be aware of this, and adjust their understanding accordingly.
Use database from #7 to demonstrate scores of current tenured faculty vs. pre-tenure faculty. Make this public to both students and faculty.
