I don't think that's it's quite the way that you guess. The extreme emotions opposing Swallow's current emotions are, of course, probably out, but I think it's more likely that she'll get the neutral emotions than even the matching extremes. Chargen not-yet-Swallow as a Tremorfoot or Fleshcrafter would be
really greedy or
really greedless, for example, suggesting that being merely a little greedy or a little greedless wouldn't be enough to qualify for that class. And extreme emotions are naturally more difficult to hold and more likely to be disliked by voters. Taking those two facts together, making the step from Hopeful->Not Hopeful will be easier than Hopeful->Really Hopeful, and at the same time Hopeful->Hopeful (maintenance of the status quo) will not allow Swallow to become a Runesmith, IMO.
So Watersinger isn't disqualifiable on that basis alone, for example, and in fact Coldhand/Runesmith are, in my view, actually harder to reach than their neutral equivalents even if Swallow has 'headstarts' on becoming extreme enough to become one of those. Stubborn is, after all,
not Really Stubborn, and I think being only Stubborn to a degree will be more likely to give Vineweaver than Coldhand.
Likewise, I think we should be more likely to disqualify extreme emotions in areas where Swallow is neutral. Neutral->Angry->Really Angry would be a more difficult set of steps than even Hopeful->Really Hopeful, let alone Hopeful->Hopeful or Hopeful->Neutral.
You're also somewhat inconsistent, disqualifying Vineweavers/Watersingers but not Thunderfists...the only reason I can think of for you to be inconsistent on this point is a personal preference for the Thunderfist powerset relative to Vineweavers/Watersingers.
If that's true, then you should say so plainly.