I dunno. There's really no need to drop-kick the remaining pillars of her faith at the moment. Let that happen when she has literally
any other lifeline to cling to (which, once some time has passed and she's gained her bearings and/or attained personal arcane power will be a thing).
There are logical reasons that apply and that still don't play into the "lovestruck boy with his head in the clouds" trope. I think any argument to convince Rhaella that her son's judgment can be trusted has to start there.
Off-hand, I see the following arguments emerging from the thread:
- We have no prospective allegiance that is awesome enough: we're holding out for something better (truth: it's just that that someone is Lya)
- We cannot bind ourselves to another political actor in this situation, because any actor we consider worth it would by virtue of land and armies and allegiances be seen as the senior party (arguably true; at the very least a possible argument)
- Binding ourselves to a paramount would be unwise because of their leverage (very true, given our unorthodox maneuvering; we do not want to get hamstrung here)
- We cannot protect a mundane wife from assassination (true, but an unpalatable subject to bring up, because that would imply fundamental weakness and would not reassure Rhaella)
- Such a queen would be essentially a puppet left at home (IMHO an arguable argument, but one that might affect Rhaella due to resonating with her former status under Aerys)
- She's the engine behind our success (true, but Rhaella may well see that as Lya essentially holding Viserys hostage; Lya would be an intruder in that scenario, someone interposing herself above her station)
- We love her and we just don't care what people think (very much true, but would not impress Rhaella)
I probably missed some, so I'd appreciate corrections and input here. Still, these points should be enough to present a cogent argument, and again, nothing says we have to flat-out reject the notion right this instant.
One final point, though: unlike other prospects, Lya
accumulates. By which I mean that as current political development goes, magical might is a cachet that is growing. Also, the more powerful she gets, the greater the prestige will become. Much like "peerless in the joust and on the field" was a hell of a feather in your cap, "most powerful and influential magic user on two continents" will increasingly
mean something.
Time favors Viserys here.