I started playing in 2007. My first Alliance character was a Night Elf Druid. My first Horde character was a Blood Elf Paladin. I say this only to show a) I have been playing this game long enough to see some very weird race/class options introduced over the years, and b) I have a bias for Druids and Paladins in general.
Bearing that in mind, I am going to use some of the arbitrary/bizarre/wonderful race/class combinations I’ve seen introduced over the years to make my case why Nightborne should be able to be druids, and why Void Elves should be able to be Paladins.
In Classic, we begin with only Night Elf and Tauren Druids. The Night Elves look down on the Tauren, but Cenarius told them to permit the Tauren to be Druids (in Moonglade) and they complied. It is not clear if Cenarius taught the Tauren how to be Druids, or if the Night Elves did, but Malfurion was the first mortal Druid and he was taught Druidry 10,000 years before the First War/opening of the Dark Portal. Nightborne are Night Elves, albeit ones who were separated from the rest for over 10,000 years, but it is NOT clear if that separation happened before or after Malfurion was taught Druidry.
In TBC, we get Blood Elf Paladins. We lost the Blood Elf Paladin questline in Cata, so let me run down a bit of Blood Elf history. When the Sunwell was destroyed, the High Elves became starved for magic (hence the Wretched in Eversong Woods). In order to compensate for this, they turned to Fel magic, which is why their eyes turned green. The Blood Knights utilized this Fel magic to mimic the Light, and that’s why we had Blood Elf Paladins.
If Blood elves can use Fel magic to become Paladins and Priests, I can’t see why Void Elves can’t use Void magic to become Paladins (especially considering they already have access to the Light through the Priest class). Now, at the end of TBC the Sunwell was restored, but until that time Blood Elves were using Fel magic, which is why Blood Elves can also be warlocks.
In Cata, Darkspear Trolls were arbitrarily given the Druid class to counterbalance the fact that Alliance were getting the Worgen (aka Gilnean Humans) which could also be Druids (but they are Humans who were infected, which is why they are werewovles, so how does this make them Druids??). I think the logic for the Darkspear was that the Trolls could use voodoo to transform into animals already (see: Zul’Aman), and were familiar with Nature magic through Shamanism, and so the Mulgore Tauren taught them how to be Druids.
It’s also worth mentioning that it was in Cata that Night Elves began being able to be Mages. They had no access to Arcane magic prior to that.
In Legion, the Horde gained a new sub-race of Tauren, the Highmountain. Since the Night Elves/Cenarius taught the Mulgore Tauren, I am not clear how the Highmountain Tauren became Druids, unless Cenarius taught them as well. Or was it arbitrary because they are Tauren?
In BFA, the Horde gained a new sub-race of Trolls, the Zandalari (who we helped in Zul’Gurub, prior to Cata), and the Alliance gained another sub-group of humans, the Kul-Tiran, who can also be Druids, like the Gilneans who became Worgen. (With the Gilnean and KT human races being Druids, why can’t Stormwind Humans be Druids??) If the Mulgore Tauren taught the Darkspear Trolls to be Druids… WHO taught the Zandalari???
So we have Blood Elves using Fel magic to become Paladins. Why can’t Void Elves become Paladins? And if Blood Elves can use Fel magic to gain access to the Light, why is it such a stretch for Nightborne to be Druids, like the other Night Elves? Night Elves couldn’t be mages originally and one day they suddenly could, so Nightborne learning Nature magic isn’t a far stretch.
Therefore, please consider adding:
Nightborne Druids
Void Elf Paladins
Human Druids
tl;dr: I see this as balancing out what we already know: Night Elves can be Druids (remember: Suramar was a Night Elf city), Humans can be Druids (see: Gilnean and KT Humans), and Void Elves should be able to use Void magic to become Paladins the same way the Blood Elves used Fel magic to do the same.
Feel free to disagree with me, but I hope Blizzard will take my evidence into consideration.