I run a daytime buffet, 11am -1:30pm as well as a night buffet on Wednesday and Sunday. A buffet can be profitable but you have to seating for at least 50 people and be able to turn over your tables at least once. Your food cost are going to be fairly high, mine run almost 40% on buffet, but my labor is in the low 20s.
Running a buffet properly is not easy, keeping pizzas fresh, having 25 factory workers come in at once, and trying to time when to put in pizzas for your rush which is never at the same time. My suggestion is not to do it half *ss if you are going to do it, commit and buy a nice salad bar and warmers for your pizzas.