I don't think you'll have any problem fermenting in cornies, in a small freezer. I actually have a lager right now fermenting in a sankey in a small fridge, and I move it to my kegerator for the lagering step. Done it many times.
Lagers are not overly complicated....my typical lager involves fermentingat 50-55 degrees for between 20-25 days, then bringing the temp up to 65 for two days (diacetyl rest), then transfering in to keg and dropping temp to 39 degree for two months (Longer depending on style), and gassing it up at the same time. Biggest concern is being able to control the temp of your fridge freezer accurately.