This is just a non-expert opinion here...but I wouldn't want my beer to be stored long term in temps that will swing from 50 to 70 degrees. Anything is possible though. There are diy threads where people make seperate chambers in their keezer, but it's labor intensive and somewhat technical, so if you're a diy guy have at it, but if you're not inclined, then I'd just get a dedicated fridge/freezer for your cold storage and keep the other one for fermenting. I currently have 3 freezers in my garage. One is a freezer, the other is cold storage for beer/yeast/grain, and the 3rd is my fermentor. I also have a dedicated kegerator in the house that holds two kegs and guess what?
I want another freezer to lager in!
First Brew was thanksgiving 2011, I'm at 100 batches and counting (as of 10/27/2014), and ran out of room in my signature to list them all.