Allied Races
If you pre-purchase Battle for Azeroth, you will be able to begin your journey to recruit these Allied Races:
Lightforged Draenei, Highmountain Tauren, Void Elves, and the Nightborne.
The details and timing for release of other Allied Races are still being figured out.
so, with all the info released already i was thinking what they could do for the last two allied races, since it ill be mid xpack, (assuming complete questline achieve and get revered or exalted as well) having them start at 20 didn't make to much sense, which led me to think of an idea for how they could be released.
basically your new allied race is a bodyguard/companion of your current char, as you quest get rep etc, you unlock a quest to investigate the experimental old god
during that quest you loot an item or run off to the side (if other requirements are met to make the new allied races) and start another questline

somewhere in that questline your companion starts shouting "omg it's taking over my mind" grabbing his head, screen fades to black...to char creation,
you make the new allied race, and the starting area for him is trying to rescue your char escorting your char on a cart to the exit of the old god lab) like...the BG.

during this you have to fight enemies, pick up a couple more allies (acting as tank/healer/dps) and just like the 110 boosts, you learn your class/spec, by having to keep the unconscious body of your other char alive, whether by tanking, interrupting or healing.

your new allied char then outside leaves your char in the hands of medics, and continues the investigation

when you log back on your old char you are in the medics camp having just woken up, your companion MIA
(and whatever ilvl your companion got up to, how high his exp got -was he 118 or did you do enough quests to get em to 120?) is what level / ilvl your new allied race has (generic ilvl whatever gear, nothing fancy)

but while they're still a bodyguard the gear you equip on them raises base damage healing hp etc, and gives them an ability for each slot (thinking grounding totem wind shear etc, and higher ilvls lower cd, so instead of a 1m interrupt from follower it's down to 10s?)

ofc, other way it could be done is to start at lvl 20 like other races...but i think something this involved would create way more immersion, i mean you would KNOW exactly where your char came from, his history, what he died from while questing, etc...not just, a mysterious new adventurer comes into the world...
but you teach him how to be a champion leveling him up, then he gets mind controlled(by the person behind the keyboard lol)
and becomes an actual adventurer, everything previous was a setback/training for him to be a full adventurer

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edit, i mean...the details themselves are still being worked out, i think it's likely it won't simply be a 'create this new char once you meet the requirements'
because those details would be easy to work out, need x zone achieve, and y rep, same as other allied races..