I agree that a smaller ski is needed in times of thinness. I don't think a one ski quiver exists. I have a 122 SkiLogik Bomb Squad that's perfect for those massive days. They are too heavy for really long days in the hills. I just got a pair of SkiLogik Yetis. They are 105 under foot and super light. I haven't skied them yet but the previous version that I was testing were great in mixed conditions and the soft that you encounter in the trees even when the wind had its way with the alpine zones. I also have the SkiLogik Piton which is 94 underfoot. This is more a mountaineering ski but was my go to ski last year. There were so many "bad' days, snow-wise last year that I could rarely justify the extra weight of a big ski. I've also skied the Howitzer which is 110 underfoot. This was my go to ski two years ago when we had reliable snow almost every time in the hills.
I think if you had to have one ski 95-105 would be the range that I'd go with. For those deeper days you'd get better penetration into the pack and therefore more faceshots. After all isn't it about how many faceshots you get
For the sparser days you'd have a better time dealing with the mixed conditions that you will certainly encounter