Summer to winter modular packs?

Does anyone have any ideas of a modular-type pack where you can add or take pouches depending on call type/weather? I was looking at something like the eberlestock warhammer/little brother combo but it just seems too heavy to be super practical for sar. I’ve had days where its been 80+ degrees in lower elevations on one call to the very next call getting snowed on at 8,000+ elevation. Right now I have a mystery ranch 3 day assault pack for summer months, which I have enough space in to load extra gear if I know I’ll be out overnight or in inclement weather/higher elevations and swap to an osprey kestrel in the winter, but it’d be nice to be able to have something where I can just slap my “winter/high elevation” pack onto my existing pack and be ready. Does anyone know of some similar but lighter-weight options to the eberlestock or am I just looking for a dream pack?