The new stuff people are doing (myself included) with 3/16 tubing and cheap diaphragm vacuum pumps is pretty cool. I think it'd work really well in marginal climates like Tennessee. First off, it's super cheap. $100 for a pump and tubing is like $45/800'. Second, with vacuum and tubing, the taps stay fresh WAY longer than hanging buckets. So, a guy in Tennessee could tap at the end of December and just leave the vacuum running whenever it's above freezing. If you got a couple cold nights here and there you'd probably get good sap runs afterwards.
By the way, there's some easy math to help figure out how big of a cooker you want. Basically flat pans usually cook off a gallon per square foot per hour. We used to run a setup with three pans totaling 25 square feet. We'd run it 24 hours a day during the big sap runs, but generally you don't want to do that. So, you can figure a good sap run to be 1 gallon per tap (might be different in your area). If you've got 50 taps and you want to cook it all in 8 hours, you'd need something that can cook 6.25 gallons per hour, so a 2x3 or 2x4 flat pan setup would work well..