And are you thinking of any particular scenarios, or just trying to cover all bases?
I've just washed out two spare backbags, and am thinking of this. (We always go around with backbags anyway, so have loads in the house.) I've had an emergency hospital bag for ages, because of various health issues, and unpleasent experiences of ending up in hospital with nothing with me. That really only has some toiletries, a change of clothing, list of medications, a power bank and charger and a snack in it. I'd like to cover more bases - partly insipired by recent events in Whaley Bridge (I live nearby).
So far I'm thinking basically the same as the hospital bag, but add in copies of some important documents (insurance details come to mind!), a small amount of our daily medications, some first aid stuff. I'm more concerned with hasty evacuations, fire or flood, than I am with less likely scenarios that would have us bugging out to the Peaks!