What a mini needs in the winter? Warm water. Food. The end.
Ha ha, but really. Minis are built very hardily and can withstand Crazy weather situations! You'd be surprised! One of mine has a medical condition, so I blanket him but only him, and only when its under 15degreesF. Otherwise, they are all running naked outside in the shoulder-deep snow all day. As long as they have hay, they're really fine. I know some folks who don't blanket their minis AT ALL, and have them outside 24/7 in REAL bone-chilling weather compared to my area's warm one-digit degrees!