The same courses, the same methods, the same feuds continue until someone dies or retires. More-frequent moves, in my view, would be beneficial for individual scholars, who would be exposed to the stimulation of different kinds of students, colleagues, and courses. Such mobility also would benefit departments, which would start to look less like clubs and more like working groups in business. My own batteries were recharged by moving, and I believe that departments fortunate enough to have fairly frequent turnover become more lively places as interesting new people arrive each year. A contract system would spread these benefits more widely.
Pay is a second advantage.
Universities have long underpaid most of us, a practice implicitly justified by the allegedly incalculable benefits of tenure. Having given away tenure, we might legitimately demand to be paid like other professionals. Renewals of contracts would become occasions for serious negotiations. A scholar reaching the end of a contractual term might naturally take that opportunity to see what was available elsewhere. Collective bargaining might turn out to be an appropriate model in some institutions.