San’layn as allied race. 
I think Dark Ranger customizations for Blood Elves should be a better choice than San’layn.
To me, Dark Ranger could be a new class. But I’m pretty sure we won’t get it. So it’s better to get them as customizations for Blood Elves to give them a second visual theme.
San’layn can have more stories to tell us with the Horde. More lore to discover on them.
I really don’t think the San’layn fit as a customization alone. They really do need their own racials and such. They’re not Blood Elves anymore.
Dark Rangers I’m conflicted about as they could be customization, their own race or a class.
They’re not blood elves anymore as they’re undead. They’re not as far away as the San’layn though and while I personally don’t buy into them being a singular class, it wouldn’t be hard to make a class based off the archetypes we see of them in game. Only issue I feel with them being a class is the few races it would be available to namely the Forsaken, Blood Elves and Night Elves. Those are the only races that have anything to do with Dark Rangers and I’m not super interested, personally, in Alliance Dark Rangers. Didn’t like it in Darkshore, still don’t.
Dark Rangers are a Horde thing since WoW started. I feel like it should stay there.
The same things that make them a good option as an allied race also makes them less likely as a pure customization. They have a lot of unique character and concepts that can seperate them as their own thing.
That said, there are a few things that make it make sense to at least push for them as a customization option.
They are already making ‘subraces’ via customizations, no reason to exclude any if it can work.
Allied Races might never be a thing again, the system had a lot of flaws and Blizzard might not want to deal with it again, especially since they are in PR mode and might not want to revisit ‘failed’ features.
Racials might not be as big a deal in the future. They are one of the main things driving the faction spillover, another being wanting to have a large pool of players to play with. They are shaking that up by allowing some crossplay between factions. A mass adjustment of racials is one of the next logical steps.
There is still hope for a refined Subrace System that changes Racials/Voices and potentially class selection.
For one, the Ranger Class does have a lot of meat to it.
It’s a hunter with undead/dark themed abilities. And we have seen that on Hunters already and they now can tame undead pets.
Another Mail/Ranged Weapon/Pure DPS class is really not needed.
Dark Rangers also already exist as a Blood Elf option, even if only for NPCs. So it would just be a simple flag. And they have been shown to be more “Classes” then just Hunter, even if limited.
Not to mention they make perfect sense for “Class Skins.”
As for a Race, they aren’t majorly different from either Blood Elves or Forsaken. So there’s a very low chance of them being added as their own race other than to save time.
Another bonus for the Customization idea is they work with other concepts for Blood Elves very well. Face Paint/Scars/Torn Ears/Red Eyes/Edgier Haircuts/Darker Jewelry Options. And those all work with other “Customization Subrace” concepts as well like San’layn and Felblood. (Not to mention Blood Elves need a vastly different visual option of some sort.)
So there’s a lot more ‘pluses’ for Dark Rangers as a customization option IMO.
In Short.
San’layn make a lot of sense as an Allied Race, but can work as a Customization/Subrace if done right.
Dark Rangers don’t have enough to be a full Race/Class, but work well as a Customization/Subrace or Class Skin.
Dark Rangers actually SHOULD be their own race and class combo.
Yes, there’s lore to craft.
I think such efforts would only be rewarding if done right.
JUST the story angles on the Forsaken since the arrival of Calia alone for the Forsaken lore as a whole would be amazing if they’d just work hard and actually try to do their best.
Actually I’d imagine Dark Rangers wearing Leather, and by the lore they have a stealth like ability. So they’d be more like a ranged weapon wielding Rogue with Necromantic abilities.
That being said, I don’t expect any new classes any time soon, we don’t need a fifth Leather class at the moment, and I absolutely hate the idea of Alliance Dark Rangers. So I’m all down for them to be blood elf customization.
…
Anyone who thinks Dark Rangers and San’layn can or should be available Alliance side is missing the point of each.
…
Okay, now I know why.
It’s pretty hard to find any cool races hinted at in game that would have a realistic chance to join the Alliance.
Other than my idea of asking Blizzard to buy a license to add the Legend of the Five Rings Great Clans variations of Humans and start to allow cross race … um, interactions…
Intimate ones.
Because the Crab Clan’s Hiruma family would utterly LOVE as an entire family the idea of both Night Elf Scouts as well as Dark Rangers… For VERY different reasons…
Yeah, there are certainly fewer races that are likely to go Alliance vs the amount that would realistically go Horde.
There are a few that could be pretty neat though, like Furbolg.
I’m honestly not so sure.
With the way WoW is normally written, the vast majority of races are usually at least Savages, like the Orcs.
It’s a writing trope that Blizzard would normally be justified for having, at least until one realizes that the majority of Azeroth is populated by, to most, bullies.
The existence of real and actually developed societies, even to say Greek or Roman standards WOULD go Alliance. However, we haven’t seen any yet, due to the fact that even fighting a no access to magic society would STILL be a major military threat.
There are a group of Furbolg that are allied with the Alliance anyway: the Stillpine Tribe.
So it’s not like it would be that odd for them to become playable.
Tribes of Furbolg have been quite cordial/allied with the Night Elves for thousands of years.
There are other examples of potential races to join the Alliance, but that’s one off the top of my head.
That explanation changes things for me then.
Thank you for the post and info.
However, do you see that for most Furbolg, these other ones are pretty much JUST targets?
Can the allied race system really be considered a failure?
It was pretty popular in general and was one of the better features of BfA. It also opened the door for certain races becoming playable when they didn’t have a chance as a core race.
Certainly, the system has flaws and valid criticism, but I wouldn’t really call it a failure. I don’t really see it as something to be abandoned, but refined in the future with some of the criticism addressed and changes made.
I’m still of the opinion that we’ll likely see new races in the form of core and allied races, in terms of how we unlock them.
Just my own personal opinion, of course. 
No problem. 
I see what you’re getting at though, yes.
If you’d like to see more, check out Fen’s wonderful thread on the topic!
The single biggest complaint Alliance side is that the AR’s given were “just” different versions of already existing races.
Lightforged Draenei are still Draenei.
Dark Iron Dwarfs are still Dwarfs.
Mechagnomes are still Gnomes.
The Horde got ONE such race, the Mag’har.
Otherwise, it was Vulpera, …
Yeah, that’s the usual issue A side.
Balancing issues to unlock each, both being unequal as well as not fun was the other major issue.
Edit:
Sorry, High Mountain Tauren, too. So that’s at least two.
Please see below.
Taunka would have been FAR better instead, however, I do get at least somewhat why it was HMT.
HMT are just Tauren with moose antlers. I know they get a cool culture and all, but I mean visually.
Okay, so I’m wrong.
The issue I think overall was that ANY of the new races were tied to prior ones.
Yes, I know that’s not by itself an issue. However, since when has Blizzard ever seen fit to truly do right by the races past Orcs versus Humans?
If you look at the first four ARs, that seems to have been their original design goal. Basically quick “premium races” to force time played metrics. It wasn’t until later that they started getting interesting, not counting the half-hearted changed model that Nightborne got.
My issue with Nightborne is that Blizzard seems to be making a version of Night Elves that they like.
I would not be surprised if NE’s get written out of the game and NB take their place.
ANYWAY.
Halloween.
All year.
I’m so down for a female San’layn at this point.
My birthday is the great haunting day.
So, yeah… I’m biased. At least in a good way!