If I truly am allowed only one bike, then yes. My Farley runs 27.5 x 4.5 tires normally but I believe I could get new wheels and skinnier tires for summer riding, so I would have some variety. Around here (Wisconsin) we normally have many months of snow. My road bike sees the outside roads maybe 6 months (depending on road conditions) but my fat bike can be used all 12 months, in all conditions.
Is it the ideal bike for all conditions? Oh no. I need to have my fat bike, my MTB and my road bike for the variety. When I'm riding my fattie on the roads (when the roads are snowy or icy), I miss the speed I get w/the road bike.