The only piece that's maybe a little dicey is the single load balancer/gateway. If there's a hiccup in that, then everything goes down.
But I've only blown up my cluster once in like 8 years or something, that's not too bad. It was a learning experience :-)
What other kinds of isolation do you want? I can see maybe a separate staging environment if you want to test gnarly things like that ahead of rolling them out to prod. And I guess maybe they can eat eachother's resources if you don't have request limits nor auto-scaling enabled.
But I'm cheap and managing more clusters sounds like a pain. Then I'd have to deal with more kubectl credentials and what not too.
