I've done something similar, in that I've had PCs that have purchased "burned out" Ioun stones... the ones that ran out of whatever magical power they originally had and turned grey... and then had Continual Light cast upon them. Because even though the burned out grey Ioun stones no longer had...
No. Double no. Triple no.
She is her own DM. She is going to learn her own best practices. She is not going to be perfect, and she is not going to be the best DM for how each and every one of you wish to play the game. Heck... I've seen enough of your posts complaining about your players...
The Necromancer is like the Psion and the Warlord... every person has a different idea about what it should do and how it should be done. And every Necromancer player will have different things that they need their animated minions to work and look like.
Are skeletons/zombies animated purely...
Hopefully each of us will be able to take this one data thing and use it to spin-- I mean "prove"-- whatever it is we want to believe and say regarding Wizards of the Coast and Dungeons & Dragons.
Needless to say... the game is still here.
Until I actually play any of the three Dragon Delves adventures that were listed as possible for solo play as a solo play player to see how their solo play rule suggestions actually work... I will not bother trying to "fix" them sight-unseen. Heck, for all we know a veteran D&D player could...
And the answer to this is that they should be in any specific 5E24 game if that game's DM wants them to be and makes/finds a Half-Elf species design to incorporate into it. If specific Half-Elf game mechanics are that important to that DM, then that DM can add them.
But if the question is...
That's not the point. The point is Vex and Vax could have been half-elves in CR Season 1 and been played as half-elves and been treated as half-elves... even if the couple of racial game mechanics written on their character sheets were human ones or elf ones. You don't need specific game...
Could be done, but never going to be done. At least not within the 5E paradigm.
The D&D advancement game is about Class. That's it. Class is all that matters. Species, background, feats-- all minor flavor bits by comparison.
They all stink and do not identify a gosh-darned thing.
BA Dash? Is it an orc or a rogue or monk? I guess this ability insinuates they are one and the same.
Perception skill proficiency? Is it an elf or pretty much any other character that selects the most popular skill in the game? The...
I'd let you use an Unseen Servant in this way even if there weren't "rules" in place to allow it. In fact, the Servant wouldn't even be just barely passable, but actually a fairly good drummer at the beginning. And as the Bard leveled, the Servant would level up their drumming skill too...
I for one do not find a single species whose mechanics are appreciably meaningful... especially not when you bury them under 20 levels worth of class mechanics. ;)