I do like that idea. It seems a lot more "him" than becoming nunh.
(Though I wouldn't rule out him becoming leader-not-nunh of the tribe at some point, especially if he gets involved with the Allagan ruins, but not within the scope of this story.)
I do have to wonder how much character development they could work in for him in the hypothetical "Corvos as relic zone" though. If it's outside of MSQ they can't have him making any life-changing decisions that would alter his ongoing status in the main story. Unless they're planning to write him out of it...? But that's getting to several layers of hypothetical at once.
I do have to say though, having learned that he got (essentially) pragmatically disowned as part of an effort to cover up the tribe's links to Allag, that explains a longstanding oddity as to why he was ever allowed to go off and become a Sharlayan historian instead of sticking with the tribe and probably being nunh by default, if - from what we previously knew - they need to pass down the Allagan Eye and the previous generations' bearers were his father and grandfather.
I'm not sure that he can't pass it down, though he did say it was happening less reliably in recent generations. However, given all that has happened with the tower, he may feel that the tribe have fulfilled their duty by maintaining it to this point and it no longer needs to be passed along with the same urgency.
If it's voluntary, is it slavery? But yeah, it's weird to us, but it's just a completely different cultural concept for them. I get the impression that they probably just regard it as more of a practical matter.
Maybe it will change with time, at least for the less isolated tribes, as more members interact with other cultures that have more of the "monogamous pair" view of relationships. (It certainly seems to be rubbing off on M'zhet Tia even if he does declare his intent to become nunh in the same breath as trying to flirt with J'olhmyn.)
Certainly Raha, having spent so much of his life away from Seeker culture, is unlikely to regard it in the same way as someone who has been in that culture all their life.
Of course, more traditional Seekers might find it just as weird, or even selfish, that someone would choose to take a dedicated partner instead of doing what's best for the survival of the tribe as a whole.
(Different clan, but there's a bit in the Postmoogle quest about Moon Keepers where - aside of everything else going on - Mauh remarks that it's unnatural for someone to take a single partner. Without delving further into it, you can instantly see they just have a different attitude to what we would think is normal and expect people to aspire to.)
Overall it's just an interesting alternate mindset that the writers have invented and then never explored, or only poked at nervously while apparently hoping people don't look at it too closely and realise what they're talking about.
On a separate note, while we're generally on the same wavelength regarding our favourite catboy, you seem to have some interesting takes on certain events...
I seem to have missed this "comic scene" with Lyna. I don't recall her having anything more than the understandable amount of confusion on discovering her grandfather looks the same age as herself. Or probably just having to get used to seeing his face at all, really, when he's been a shadowed mystery all her life.
And all that happened with Aenor, as far as I recall, was that she tried to flirt with him and came to the conclusion that despite his young appearance he talks like an old man.