To elaborate on my thoughts on the deer; My problem with the deer isn't that its boring - I love having more "boring" animals - it's just that its not common nor unique enough to warrant being "needed" or "essential". Wanted, sure, but far from needed. The niche of a deer in NA may be absent, but there are far more interesting, unique, zoo-relevant niches that are too - looking at birds alone (which NA still has none of) native wading birds, waterfowl, and to a lesser extent game birds are all just as, if not more common in NA zoos than any native deer species - and would arguably add more to the game's overall roster as well. I think a NA deer would be a solid addition and I've come around on the white tail after getting into further research on its captive presence. Although I do think giving Asia a deer would be more beneficial as they seem to be far more relevant to zoos over there.
In short, I don't think a NA deer is essential, but I'd be open to it... if we had another year or two left - and if we do, then yeah, sure, why not. That's just me though.