Uh, isn't that why wild spirits don't grow? Because their specific niche is pretty limited.
I don't think it is. It's not because their niche is pretty limited, it's because their niche isn't good enough. Being bound let a spirit get more breadth by going outside their niche
and let them get more specialisation by learning more who they are. The first doesn't mean the latter.
There
is an argument, however, that having more breadth can help as we know too little of what actually helps.
I mean... sure, if we categorize "Foundation Building" qi as Not very useful to useless, then getting it would not be as beneficial as other choices. Fortunately, we don't have to have to categorize it that way.
I mean, I can categorize the moon qi option as the useless option as well. It is more of the same qi that she is, which won't change anything that's she's done and won't provide any benefit outside of what Sixiang has already changed. It could bring her back up to where she was, or slightly increase her power which goes from "useless" to "Not that useful."
I mean, it's an assumption that having access to moon qi will make Sixiang stronger in her niche rather than simply recharging her to the point that she should be. Why would more moon qi mean make Sixiang more focused on her niche? What change would more moon qi provide Sixiang? It seems strange to assume that Moon qi will make Sixiang more specialized rather than get her back to where she was.
Contrast that with the other two options: One provides more potent qi and one provides better foundation building qi. We could characterize one of those options as being stronger, and the other option as having enough of a foundation to handle reaching beyond your limits.
It's a standard troupe that having a better foundation allows for one to better leverage their advancements, and if this is Sixiang making an advancement in "domain" creation than having a better foundation will allow her to better leverage that advancement and make the most out of it. Foundation doesn't necessarily mean more breadth, but could also mean a deeper, more solid "ground" upon which to continue building upwards. For Sixiang that could very well mean something more tangible to anchor herself and her pseudo-domain to.
So I think that your characterization of Foundation = breadth is inaccurate. If you're unsure of what foundation building qi means in this context, then why assume and characterize it as something "not that useful" or even "useless?"
It's not an assumption that 'Moon Qi' would make Sixiang stronger in her niche. My argument isn't that Foundation Qi does nothing, but your argument seems to be that Moon Qi does nothing. There is plenty of people like
@Ayashi or
@wingstrike96 who believes Foundation Qi actually is key to advancement, or that Breadth is good in and of itself, and those are probable belief.
Obviously Foundation Qi will give a better, more solid ground to continue building upwards. That is what foundation is. However, the argument that 'Foundation Qi' is
both Foundation and
Specialised to Sixiang is ignoring the both Ling Qi's belief about the vote and the meta-narrative of voting itself. Likewise, Foundation Qi won't 'make the most out of it'. That's Potency. It's back to the argument we have had in every single ambiguous vote where "This option is actually all the options". No it isn't.
Foundation Qi is best for foundation, Moon Qi is best for Sixiang's own niche, and Potency is best for actual Potency. There is no reasonable argument that Moon Qi is better for foundation, or that Zeqing's site is better for specialisation, or that Foundation Qi is better for Potency.
This means that Zeqing's site will have the most potent effects, moon site will have the most 'improve in her own niche effect', and Foundation will have the most 'grounding'.