And a house cat the size of an elephant, of course.
OK, that might be a bit much - you’d never be able to read a book or use a computer again, and I’d hate to be the one to clean THAT litterbox.
But one the size of a full-grown Siberian tiger, but with the nature of the sweetest marmalade kitty you’ve ever known - that, I could handle.
Actually, if it comes down to it, anyone remember the experiment with breeding foxes into domesticated animals? I would fund something that preserved tiger (and other rare cat) habitats, to bring them away from the brink of extinction, while simultaneously selecting some of those animals for domesticability (is that even a word?). 10 or 15 generations might well yield something that could do as a housepet for an experienced owner.
Then of course I’d need to have a big enough country estate to let Mister Fluffikins and Mrs Mittenpaws wander around, with enough mature trees to serve as scratching posts. Only solid hardwood furniture inside, of course, and the house would need to have inside balconies / shelving to serve as tiger-safe lurking spots, ideally some place where someone’s head wouldn’t inadvertently come within reach - even sweet cats get playful, and a paw the size of a dinner plate might cause some real harm.
Of course, a cat’s purr is just about the best part of having a cat. Lions and tigers don’t purr, while cheetahs and cougars can. So, unless Tigger can be generically engineered to be able to purr, my own preference might be for the cheetah or cougar.
Mustn’t forget a real, safe, permanent cure for cat allergies - that’s a requirement. Hell, I’d spring for that even without the domesticated big cats.
A tiny elephant would be pretty cool - but we’d need to be careful of excessive downsizing and health effects (e.g. those “teacup” dogs and so on, and breeds that cannot reproduce without medical help). If a golden-retriever-size was the smallest we could get and have a healthy elephant, that’d be OK.