So of course customization is important. It's cool as hell. It makes you feel like it's your character instead of just some random copy and pasted one.
...however...
If the choice was between getting one full race each for Alliance and Horde, and... Straight up unlocking all NPC races as-is under "Recruits"....
I dunno man, I think id take the NPCs.
Especially if the new races ended up being some request-adjacent bullcrap like Lightforged, Void Elves, and Highmountain Tauren were...
For clarity:
OPTION A: Two new races, one for Horde and one for Alliance. Dracthyr-level of customization, voice lines, racial abilities, heritage armor, starting zone, transmog enabled.... but it's low-requested races like Yaungol or Jinyu or something. Still cool, but niche and not your first choice.
OPTION B: "Recruited Races". Nearly every sentient race, from Nathrezim to Venthyr to Ogre to Aarakkoa to Naga, but completely as-is. No new voice lines, one shared set of racial abilities, no specific home aside from the embassies, no heritage armor. Only as much customization as they already have, plus transmog. Each can eventually still be added as a full race.