I just don't see you getting wide buy-in for this idea. I don't think it's a crazy idea or anything, it's just too contrary to tradition to get sufficient support from the wider consumer community.
The challenge is, the D&D "tradition" has been fantasy racism. The D&D Elf "race" is a showcase of what racist theories from the 1900s look like, including "subraces", with a fixation on racial essentialism, "biological" superior and inferior Intelligence and Strength, obsession with eye color and skin color, demonization of the wrong skin color, and even occasional comments of about race "purity". The traditional Elf race is the most prominent and elaborate example of this kind of racist worldview.
We all understand that this is a fantasy game. But the structure that is mapping out these racist boundaries comes from reallife, and is ... less than great.
It cannot be that D&D 2024 continues onward as "that racist game" in the eyes of the public at large. It cannot be that once in a while we stumble across a stray sentence of some truth to the accusation.
In recent years, WotC and the D&D community are making serious efforts to find and remove all traces of racism and racist thinking. Sometimes the efforts come across as clumsy. Apparently the Spelljammer designers didnt realize that the Hadozee description and illustration were problematic, and perhaps oppositely replacing a "half-elf" with a "drow" might be an overcorrection. Nevertheless, it is vital that every trace of racism vanish from the game during this playtest period, so that we D&D fans never have to deal with racism again or accusations of racism from a less informed public at large.
So far, the UA playtests introduce judicious and aggressive updates to solve worrisome areas. The nomenclature now clearly refers to "species" rather than the ambiguous buzz word "race". Ability improvements decouple from species. Any Humanoid species can exhibit light or dark skin and be of "any alignment". Backgrounds are a silo for cultural features. And so on. It is still a work in progress. As far as I can tell, the most difficult aspects of the D&D tradition seem to be resolving. There are debates about where the lines are − what is or isnt a problem. Virtually every one is sincere about the effort. We all want the D&D game to be awesome − today and ten years from now.
The Elf is too human. Reallife humans self-identify with Elves. This is a persistent D&D phenomenon. The game needs to describe the Elf with the same sensitivities as when describing the Human species.
There cannot be Elf "subraces" in D&D 2024. Likewise there cannot be Human subraces. It is too close to reallife racism.
The term Elf "lineages" cannot mean subraces.
A core species in the core rules in the 2024 Player Handbook must lack any trace or thought of racism.
The previous edition, D&D 4e attempted to split the Elf traditions into three separate species: Elf, Drow, and Eladrin. I consider this valid, because they would be separate species. But the community felt it too important each of these are equally an Elf, and equally members of the same Elf species.
Now the playtest is going the opposite direction. There really is only one Elf species. The diversity of Elves are truly, fully, equally, and miscibly, members of the same Elf species. There honestly are no subraces. No racism. An Elf is an Elf is an Elf. One species.
So, when we look at the term "lineage" we must think deeply and carefully about what this term means. The playtest gets it right. For the Elf, the lineage means an expression of an elven capacity of magic.
I think of it this way. In reallife, the human species has an instinctive capacity of speech. Whatever languages we speak are learned: culture. But the capacity of speech itself is innate: biology (neurology).
Likewise for the D&D Elf. Whatever "lineages" Elves magic are learned: culture. But the capacity of magic itself is innate: biology (sotospeak).
Elven lineages behave similarly to human languages. Sometimes a same language in a locale can persist almost changeless for centuries. Sometimes a language can shift drastically in a single generation. A speaker or magicker can learn a new language or lineage instead, and even forget a language or lineage.
Humans can choose which language they want to speak, especially by immersing in an other language. Elves can choose which lineage they want to magic.
The magic is innate. But the "lineages" that express this magical capacity are cultural traditions.
This spell-centered design for the Elf, escapes essentialist subraces and escapes racism.
