>>10475592>Imagine a 6 foot tall felineWould be an absolutely insane beast. You'd probably need to return to Miocene climate and massively expand the forests and reduce the range of grasslands so that you could get an environment similar to what supported Simbakubwa and the giant African Hyaenodonts. Amphimachairodus and Smilodon Populator are probably the closest felids can get to being Hyaenodont sized given the environmental constraints of the Ice Age we've been in since the Messinian. I was reading a paper that recently came out that said the decline of megafauna in Africa had started long before humans had the ability to hunt them and that is a big reason we don't have 10 ton elephants anymore is because of the decline of open forests. Without large healthy populations megaherbivores you can't get giant hypercarnivores like Simbakubwa that specialized in hunting rhinos and young elephants.
link to the paper if you're interested and your university gives you free access like mine does.
https://www.science.org/doi/10.1126/science.add8366