Somewhat related but the recommendation of deer doesn’t really sit well with me to be honest. I’d personally rather see anything other than an invasive species in Australia feature in zoos. I roll my eyes every time I see any of the invasive hoovestock features in zoo collections. That maybe a controversial take but I’d rather see literally anything else than an invasive displayed in our zoos.
This is an important point - and I agree with you for the most part. I suspect that this is also part of the reason that Zoos Victoria don't display deer species - but I don't know that for sure.
That said (as others have also pointed out), deer can work as a supporting act to something big like Indian rhino.
The other point I would make is that each individual species should be looked at on a case by case basis - I don't think they can all be put under the same umbrella. For example elk would take up far too much room, but axis deer or hog deer in with another bigger species isn't a problem to my mind.
Another point on smaller hoofstock (deer, antelope, bovines etc) is whether the public actually sees them as "zoo animals". I've come up with a formula to decide which side of the fence these species sit on:
Formula: Do you know at least 5 people who would knowingly eat this species?
My answers:
No: Elephant, rhino, hippo, giraffe, okapi, zebra, tapir
Yes: All other species of ungulate including bison, all deer species, all antelope species, all wild bovine species, all equine species other than zebras.
Obviously there is no way in the world that I personally would eat addax, oryx, Prezwalski horse etc - but there are a lot of people out there who would.
To me this completely puts these species out of the "enabling" criteria - and I think that criteria has a bit more weight than some of the other criteria (at least in my point of view anyway).
The "deer question" is a seriously important one though - and I'm glad you have mentioned it.