The drawback is that the yeast can go dormant, at some point below the bottom end of the temp range is the point the yeast will go to sleep until warmed back up.
There's always options to warm a fermenter up, they just haven't occurred to you yet.
Wrapping a blanket or sleeping bag in is good for a few degrees.
Putting a carboard box over the fermenter.
Move it to a warmer section of the house.....like against a sun facing wall.
Do you have hot tap water? Do a reverse "swamp cooler," put your fermenter in a larger container and fill it with hot tap water instead of ice.
Wrap a blanker around it then wrap it in christmas lights for an extreme example.
Told ya...