My guess is that this is a non-starter, but... Is it possible and humane to get a cat and make it a completely outdoor cat from scratch (as it were)? By giving it somewhere in the back garden to go when it's cold, feeding it and taking it to the vet, etc., just...all outside? (In central England, in a village or town, not a large town or city.)
The background is that we cannot have cats (or dogs or any other furred creature, or birds, or...) in the house, due to my major allergy to them. My son has a more mild allergy, but loves dogs and cats. He adores a neighbourhood cat who comes around regularly (we know who his family is). He pets him and talks to him etc., then washes his hands afterward, and really gets something from that and from the cat coming around. But we'll likely be moving house in the next year or so and he's already sad about leaving this cat behind. He has fish, but...he's more of a hands-on pet person, and specifically really wants a dog or cat. (Well, and a snake, but that's been vetoed by his mother!)
So after we move I was thinking whether it would be possible to get our own outdoor cat. But I worry that it may be impractical, inhumane, or otherwise inadvisable. I don't want to do anything that would be putting the cat in harm's way or similar.
(I'm not looking for alternative pet suggestions, but thanks.)