I think Bat-eared Foxes are largely insectivorous. They’re certainly not your typical opportunist fox.There is a very similar mix at Living Desert of with no guinea fowl and hyrax instead of dik dik so that should work. I believe guinea fowl are larger than bat eared foxes and I’ve never heard of Bat eared foxes being particularly violent towards larger animals.
“In a big enough exhibit” no just no, don’t mix okapis with gorillas.
Even if the Gorillas were totally benign and lacking in enterprise or a sense of humour, you’d end up with panicked and injured Okapis at some point.